First, to activate the cheats, you have to edit the file baldur.ini in your Baldur's Gate directory and add the line "Cheats=1" under the [Game Options] area.
After you start the game, hit CTRL+TAB to bring up the console. (CTRL+TAB again closes the console). Type in the following cheats and hit [Enter] to activate each one. Before each cheat, you'll have to enter "Cheats:", so Cheats:Midas() would activate that cheat.
Midas(): Gives you 500 gold.
FirstAid(): Creates 5 healing potions, 5 neutralize poison potions,
and a stone to flesh scroll.
CriticalItems(): Spawns all the game's critical items.
Hans(): Moves your character to a free adjacent area.
ExploreArea(): Marks entire area explored.
CowKill(): Creates CowKill spell if near a cow.
TheGreatGonzo(): Summons 10 killer chickens as allies.
DrizztAttacks(): Creates a hostile Drizzt.
DrizztDefends(): Creates a friendly Drizzt.