Hmmmm...haven't play BG for quite a while, but maybe some tips can help:
1) explore slowly, if you have a thief in your party (or ranger), try to hide in shadow and explore
2) when you encounter enemies, assuming you are traveling as a group, concentrate on one target before moving onto another; and try to attract enemies' attention one-by-one, try not to have all-out war
3) rest often, rest until fully healed, and don't be afraid to use healing potions
4) always have archers/slingers (i.e. range attackers) in your party
5) since your characters are usually at lower level, poison can kick in fast and I suggest you have some antidotes in your inventory
6) party members are good pack-rats, have them carry equipments that can be sold for gold
7) SAVE THE GAME OFTEN!!
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Long live H22A1!!!!!