Two Worlds

If you're a mage get Concentration early on. Cast it each time before shooting your magic fireballs or whatever for lots more damage.

Make sure you're not holding down the forward button to move on horseback - just press it for each speed you want to get to.

When you start the game most of your skills will be blacked out (at Level 0 as opposed to Level 1). You need to find trainers to "unlock" these skills at which point you can start putting points into them (list of trainer locations here). A lot of trainers can teach you more than one skill so make sure you go through all their dialogue options.

Related to the above, of note is the trainer in Rovint who can teach you some of the game's best skills in Alchemy (the most common way to break the game), Necromancy (powerful or hilarious depending on how you use it), and Stone Skin (excellent passive defense bonus). Head there as soon as you have 1000 Gold, it's not far from where you start.

Maleil Shrines (respawn points) will auto-cast Heal on you when you get close. If you're in the middle of nowhere and hurting, look out for one. Another trick is to lure enemies near one and fight them while the shrine continuously heals you.

Learn how item stacking works; you can stack same-type items to create a new item with better stats. But be aware that some types of enhancements will stack while some will overwrite one another, so don't get too greedy.

The best use I've found for alchemy is probably to create elemental damage enhancing gems.

The math is pretty screwy on the character stat screen; as you level up, your attack % will seem to go down when you level up (if you don't put points into dex); that's because the attack % is relative to monsters who are the same level as your character.

A level or two of Heal spell, bound to a quick key, is pretty much essential, and the Bless spell is INCREDIBLY useful, especially for the cheap casting cost.

If you wear an entire set of armor (each piece tells you the number of the set it belongs to), you receive a substantial bonus to your armor ratings and look more stylish in your matching duds. You probably won't be able to find a whole set for a while, but if you get three or so matching pieces, it can't hurt to keep them around.

Fire Field is an overpowered spell—especially if you Overpower it. Enemies will die quickly, and it's a fairly large area of flame.

Pick locks! Treasure chests in this game almost always have something you can use in them, and are worth the Lockpicking skill. You don't need to max out Lockpicking, though; just get it high enough for your needs.

If someone sees you pick a door lock and alerts the guards, run around whatever village you're in, picking all the locked doors you can find. Then, drop most of your gold on the ground; when the guard finally catches you, the fine he asks for is dependent upon how much gold you're carrying, not what laws you've broken. Every guard can be bribed with 30% of the fine he wants. Once forgiven, pick up your gold, saunter into the now-unlocked houses, and ransack their cabinets behind closed doors with no chance of anyone outside seeing you.

Keep at least three different weapons at all times, have one imbued with spirit damage, and one being a bludgeoning weapon. Skeletons go down faster with a paddle than a sword, and ghosts will most likely be one shotted by any spirit weapon.

Do all the side quests, you get mad gear in the process and pretty much everything you do gains you skill points. Upgrade lockpick and the skill that ups your total damage first, though.

Abusing Mechanics

For equipment, you can stack items that are the same - so if you have two short swords, you can stack them to make it into a stronger short sword. Statistical and damage bonuses carry over too. By abusing this, you can end up with a weapon that adds 20 to all stats and does over 10,000 damage a hit.

Alchemy is another system that you can abuse - there are many items in the game world that add to your stats permanently whenever made into a potion (by combining it with a regular health or mana potion), and the more of said item you add, the higher the bonus will be. Find a trainer that teaches you the alchemy skill and bump that up to 10, and then start making stat boosting potions - just don't mix in temporary boosters with permanent ones. It's not as broken as it was whenever the game first came out, but its still pretty goddamn broken.

If you still want to make the game easier - there's a water spell (I forgot the name of it) that allows you to freeze enemies in place. By doing that, they can't move nor attack, so you can just wail away at them. Traps also have the same effect, and once you get higher level traps + a high traps skill, many enemies won't be able to lay a finger on you.