ADVENTURING TIPS
The reason a Thief is such an invaluable character is that their skills are essential to speedy progress. Most particularly, Hide In Shadows allows you to explore areas without giving away your presence and being attacked. In this way you can pick and choose your battles, and uncover the secrets of the map quickly. You can also launch surprise attacks using this method: once you have uncovered a group of enemies, leave the hidden character within sight of them and bring up a mage to cast offensive or tangling spells at them while still out of sight.
The usefulness of this skill depends on how good the Thief is; the percentage score is the chance the thief has to remain hidden. If the test is failed, the thief reappears and may be discovered. When the Thief gains a level, points may be allocated to any of the four skills to improve the abilities; magical items and potions may also affect these scores. If your Thiefs Hide In Shadows skill is over 100%, they will hardly ever fail and reappear, so you can have them on semi-permanent spotting duty.
The Find Traps skill is also extremely useful, as some areas are heavily trapped. Areas to be particularly careful in are: the cellars beneath Ulcaster school to the east of Beregost, the second Cloakwood area and the cellars beneath Candlekeep. You can search for traps while still hiding, if you search for a few seconds then hide again before the character emerges from the shadows. If your Traps skill is high enough to find a trap, then you can safely disarm it. However, some traps require a very high skill level and you may blunder into it even if you are looking. Pickpocket is a fun skill, but it can be very inconvenient if you are caught, and you wont earn a huge amount of money using this skill.
Dont bother trying to keep everything you find. You wont get much money for ordinary weapons and armour at shops, but magical items should be kept at all costs. Give anything magical to your character with the highest Lore rating; if they cant identify it, and you have no Identify scrolls or spells, keep it and get it identified at a shop. Youll nearly always make a profit, or have some use for it yourself. If you find inventories filling up with stuff youd like to keep (potions, scrolls, etc.) try storing them in cupboards and chests in empty rooms in Beregost or Baldurs Gate. Gems are only occasionally valuable; try to work out which ones will fetch high prices. Diamonds are the only obviously valuable stones.
Resting while out in the open is often essential, to re-learn spells and to recharge the batteries. Try to pick an area which did not previously have monsters in it, as they are likely to respawn and attack you if you make camp, disturbing your rest. This will also happen if you reload games repeatedly in an area. Before you rest, use up any healing spells you have left if anyone is injured, otherwise they will be wasted.