Lockpicking and pickpocketing
Don't worry about people nearby when you try to pick a lock on a door or a closed chest. It seems that the good folk of Aventuria doesn't mind that. There is, of course, an exception to that rule - pickpocketing. If you fail a pickpocket attempt your target will become cautious and you won't be able to try again.
When trying to pick a lock use lockpicks or hair pins - they'll greatly improve your chances of success.
Be sure to destroy barrels set throughout the game world. It's a good way of earning some money early on, and sometimes the drops from the barrels can prove to be very useful.
Search the bodies after each fight. Animals and monsters provide some ingredients, while humans and other humanoid beings usually carry gold, weapons and other useful items.
Try to talk to every character you'll encounter. Some of them offer you quests, some are vendors, while the rest can just tell you something interesting or funny.
Social skills come in handy during dialogs - the one you will use most often is Fast Talk. Etiquette comes in handy on some occasions, while Seduce is most useful for female characters - men won't use it to often. Human Nature seems to be the least useful, but it can provide some handy information like the attitude of the NPC, find out whether he's lying or not or just learn about his mood. The last (but not least) of the social skills is Haggle - you'll use it almost as often as Fast Talk and it will allow you to pay a lower bribe, buy or sell for special items for a better price. Also, with high Haggle all items in store will be less expensive.
The difficulty of the fights can very greatly throughout the game - sometimes you're in for a rather unchallenging fight with a bunch of rats, other a tough boss fight awaits you. In order to get on top of each of those fights you need to come prepared:
Make sure your characters are at full health and have no wounds.
Drink potions and use unguents during the challenging fights..
Use active pause as often as you can - take a closer look at the situation and act accordingly.
Make use of special abilities but be sure not to waste them - mighty blow that deals 30 damage is a bit of a overkill against an enemy left on 5.
Support your characters with magic. Pay close attention to their health and heal those, who are severely wounded. Tough enemies can be weakened with magic, while fireball is great at dealing with larger groups foes.
Bear in mind that you can save the game mid-combat.
The best strategy is to single out opponents rather than fighting the whole group at once.
You can have up to three companions in your party at any given time, while the rest will await you in your residence. Try to fit your party to the area you're going to explore - moving about the city you will make most use out of characters with developed social skills and someone with rogue skills if you want to pickpocket and open closed containers. In areas where you expect some heavy fighting your party should consist of fighters supported by a spellcasting character. When you need to get components off animals or plants you'll need character with high Animal and Plant Lore. It is crucial that you always bring along a character capable of healing and removing poison.
Mage cannot cast spells while wearing a heavy armor, so you'll need to find some lighter protection or just regular robes that won't impede his movement.
Each mage should have Balm of Healing and Clarum Purum at his disposal.
In almost every location throughout the game you will find encounter three kinds of workshops - an anvil, a lab and a workbench. Each of those workshops can be used to create certain items
In the lab characters with the Alchemy skill can brew potions.
Characters with Blacksmith can use the anvil to create weapons and armor.
The Workbench allows characters with Bowyer to create items connected with ranged combat.
Try to have as many characters able to use workshops as you can - the resources to create new items are quite easy to come by, especially if you have access to Animal and Plant Lore.