Advanced Combat Tactics
At some point, you will discover that simply pointing yourself at a monster and hitting attack probably isn't the best way to gain experience and avoid a lot of deaths. A lot of combat you need to learn by doing, but there are several useful tips I can offer.
Special Monster Damage
Several monsters have unique properties that might take you by surprise if you aren't familiar with them. The most frequent (and probably most deadly) property is Hollow Damage. The hollow property ignores certain protections you might have. True hollow damage ignores life and item magic (protections and banes specifically), but some monsters ignore only life or only item. Some monsters like big Tuskers ignore the protection shields provide. Some monsters are immune to certain forms of magic. Withered monsters are immune to all magic except war magic. Some other monsters are immune to drains while others reduce the potency of drains by half or more. Other monsters have the equivalent of Crippling Blow (huge criticals) on their paws or claws. You'll discover which monsters have which properties, so be careful!
Limit Damage - The Swarm
The best way to survive is to reduce the number of monsters who can damage you at any given time. Melee monsters can only hit you if they are close to you and they will try their hardest to get in next to you. If you are fighting outside, find a good tree and block some of the enemies and force a pile-up behind the ones actually hitting you. If you are indoors, find an alcove or a corner to tie up the monsters trying to reach you. If you are fighting large numbers of monsters, selectively pick which monster you want to kill. Larger monsters take up more space, limiting the number of monsters damaging you at once. Also try to limit the number of stronger monsters attacking you. Leave the easier monsters until later. Magical monsters pose a larger problem, since they don't need to be near you to hurt you. Causing a pile-up won't prevent the monsters two or three back from landing spells on you. You can still use the landscape to your advantage, but your best bet is to try not to annoy too many monsters at once. Most monsters will run away if they can't get close enough to you.
The Runaround
Hardly anyone has Missile Defense - it's just not that useful a skill. From time to time, however, you will encounter monsters (particularly Lugian Raiders) who hit very hard with their missile attacks. If you are a melee, you will take a beating from their attacks with practically no hope of evasion. Fortunately, you can force monsters to switch from missile combat to melee mode by taking advantage of their AI. Get in close to the monster (strafe on the way in using the Z and C keys) and then run circles around him. The monster's attack will miss you and out of frustration switch to melee combat. Typically, it will only take you about 5 -10 seconds to convince the monster to switch to melee combat. I use this method against Lugian Raiders, since their Hollow Rocks can be devastating and their melee attacks are easily avoidable. This tactic is also useful against high level Viamontian Knights. When a Knight is in missile mode, its missile and melee defense goes through the roof. If you use the Runaround, you can force them into melee mode, which will cut its defenses noticeably.
Pulling Monsters
When hunting outside, you will very often find a group of monsters you want to kill in close proximity to another group you don't want to kill (or don't want to kill at the same time). Running up to the group you do want to fight will usually result in you getting swarmed, so your best bet is to selectively pull monsters. Any ranged attack will work, but consider casting Imperil as a melee or missile character or Magic Yield as a mage. Even if your spell gets resisted, it will still send the monster (and usually its group) to you. Make sure you pick a safe spot from which to pull in the event you need to make a strategic withdrawal (run away). Also, pick your targets carefully when pulling groups. Casting on an Olthoi will draw all the Olthoi from a large radius on you. You will have to learn through trial and error how each monster in a pack responds to being pulled. Casting on a Virindi will send the whole group after you, but if you cast on the Virindi's pet Tusker, only that Tusker will come after you. Selective targeting can help you thin out a large spawn, limiting the damage sources you will have to fight at once. Also be aware that buildings amplify a creature's response radius. If you cast a spell on a creature inside a building, all of that creature's allies will pour in, even those well beyond the radar range. This can be especially problematic at places like the Undead Town on Aerlinthe or The Deep on Vissidal.
Melee Combat and The Shield
The most important thing you can do as a melee to increase your survival rate is to keep all the monsters you are fighting in front of you and your shield. Your shield is like a second suit of armor, but it only works against damage taken in the forward 180 degree arc in front of you. The best way to keep monsters in front of your shield is to wedge yourself in against an obstacle. If you are fighting magical monsters, be aware that your shield won't work to reduce the damage you take. Most likely, you will want to take out the magical monsters first.
Some monster types also can carry a shield, which will make your life miserable if you are a melee or archer. Just as your shield cuts down on the damage you take, so too does the shield of a monster. If you are fighting a shield-bearing monster alone, your best bet is to try to sneak around to its backside while it is casting on you and land some devastating blows. This can be quite difficult, as most of the spells monsters cast will cause them to track you and keep their shield in your way. If they try to heal themselves or cast any other spell that doesn't use you as the target, you should be able to get behind them and whack away. Fighting a shield-wielding monster with more than one person requires you to use a pincers attack on that monster. You and your friend should stand on opposite sides of the monster so that one of you will be attacking its exposed side. The person attacking the shielded side won't do much damage, but that's pretty much unavoidable.
Recovering Vitals
If you can't restore your vitals, you won't last long in any fight. Fortunately, every character is fully capable of healing himself in some fashion. The most basic way to recover your vitals is to sit or lie down. You will recover vitals even while standing up, but the speed at which you recover is increased if you sit down and increased even further if you lie down. Of course, you can't lie down in combat situations. A more practical (although burden-inefficient) way is to eat or drink. Food and alchemical potions exist that can restore all three of your vitals. They are fast to use but weigh a lot. As you will see later, the only vital you should consider restoring with food or drink is Stamina. The other two ways to restore vitals require you to have Healing and Life Magic trained. Healing is ideal for non-mages and can only restore your health. To successfully heal, you need to use a Healing Kit, which exist in a variety of qualities. Check your kit - it will list its bonus to healing skill and its healing bonus. The higher, the better! Healing costs a small amount of stamina - the more health you heal, the more stamina it costs. If you run out of stamina, you cannot heal either. Also bear in mind that the more health you are trying to heal, the more skill you need to have. If you get down below 25% of your health total, you will have a very hard time healing, regardless of your skill, so try to heal when your health drops below half. It is also easier to heal out of combat mode, so switch out before attempting to heal. The alternative to Healing is Life Magic. Unlike Healing, you can magically restore all 3 of your vitals using various methods. Heal and Revitalize spells restore health and stamina respectively. Mana cannot be directly restored, but you can convert any of your vitals into any other vital using transfer spells. For instance, use Stamina to Mana to quickly restore a great deal of your mana. You can also use magic to drain vitals from a monster, assuming you have the skill to cast the spell and beat the monster's magic defense - there are also drain-resistant monsters too! Last, but not least, you can cast spells to improve the recuperation rate of your vitals. Failing anything else, these spells will allow your vital pools to last longer.
Interception
As a ranged character (missile or mage), you will be able to do damage to monsters as they close the distance to you. However, hitting monsters as they run is not as easy as you would think. Personally, I use Arc spells exclusively as a mage because they are faster and they are better at missing terrain obstacles. However, in a great many circumstances, Arcs and missile projectiles (which follow the same path) will overshoot moving targets, especially if they are running directly at you on a flat surface. Small monsters or very fast moving monsters make the problem even more pronounced. If you want to hit a target on a flat surface heading directly toward you, you need to use a Bolt spell. Bolts travel more slowly and in a straight line. Projectiles and Arcs do hit moving targets coming up or down hills toward you and can hit very large or very slow monsters (Tuskers, Golems) on flat terrain. Archers are pretty much out of luck when trying to hit small monsters on flat terrain, so it's best to save your ammo and time your attack so that you fire the moment the monster arrives. That kind of anticipation is a learned skill and varies depending on which missile weapon you use, the buffed speed of the weapon, and how accurately you have set the slider. Archers do have the ability to switch from arcing shots to fast, straight shots using the options menu. If you properly map keys to switch between arcs and straight shots, you can hit moving targets with greater ease. However, that's a quite complicated skill to master.
Fighting Bosses and VoD-style Monsters
Many of the new generation of monsters and quest bosses are a major pain to kill, and rightly so. To counter all the advances in weapon damage and imbue tinkers, these type monsters have very high health and resistances, in addition to high offensive and defensive skills. Many have very quick regeneration too. The only effective way to kill monsters of this type is to thoroughly debuff them and use the right weapon. Melees and Missile users usually have a much easier time hitting a monster than mages do (partially because non-mages hit faster), so mages will want to start by casting Magic Yield. Then Imperil and Vuln the monster (using the appropriate vuln and only using Imperil if you have melees or missiles in the group). Most bosses require a Fester too. If your group is getting hit too hard, consider debuffing the monster's Strength and weapon skill (usually Unarmed). If you are the mage responsible for debuffing, carefully watch the monster and recast as necessary. Attackers should switch from the usual Rending weapon to an Armor Rending, Critical Striking, or Crippling Blow weapon, since vulns overpower Rending weapons. Mages should use a Slayer weapon (Assault Orb, Gaerlan Wands, etc) if available.
There are a couple big exceptions to this strategy - Aerfalle, the Burun Kings, and the Platinum Mountain King. Each of these monsters will dispel any debuffs you cast and then cast the corresponding counterspell. For example, if you Imperil Aerfalle, she will counter by dispelling and then cast Executor's Blessing, increasing the fight time a great deal. Your best bet is to use Rending Weapons and only use damage spells.
Dodge, Man!
The best way to fight a magical creature is to avoid its magical attacks altogether. If you are an archer or mage, this means learning how to dodge war spells. The basic principle is to use the strafe keys (Z, X, C) to move yourself out of harm's way while continuing your attack. For mages, this ability is quite simple. Once you begin to cast your spell, use a combination of X and either C or Z (not both at the same time) and you will slide around. When you finish your wind-up, your spell will fire. War spells do not track once they are fired, so as soon as you see the monster fire off the spell, move a bit and you should dodge the spell. Archers have a harder time dodging spells because beginning the sliding process interrupts your firing. This is especially frustrating if you have your accuracy bar all the way to the right, making your aiming time very long. Sometimes you will just have accept having your shot interrupted, but your best bet is to begin to slide just after your shot leaves your bow. Also be aware that sliding stops 'Automatically Repeat Attacks', so you will need to select an attack height again when you finish sliding.
Melees have the hardest time avoiding enemy spells because they have to be so close to the enemy to land hits. Most of the time, you will just have to eat whatever spells are coming your way - because you are so close, strafing is largely useless because there isn't enough time between the moment the spell is launched and the moment the spell hits you for you change your direction or speed. Putting space between you and the caster does increase your chances of dodging, but it's still not an easy process. Your best bet is to use the landscape to your advantage. War magic can't go through obstacles, so you can use rocks, trees, and walls to shield yourself. If you are fighting on the landscape, before you pick a monster to pull, find a nice tree or rock to stand next to. When the monster begins its spellcasting animation, slide behind the rock or tree so that the shortest line from you to the monster goes through the tree. The spell will harmlessly hit the environment and you can then continue the attack.