This page lists the various strategies that I have found to be effective. Some of them however, may have been disabled by the BGII patch. You can still have fun finding out which ones…

'Fake Talk'
The fake Talk strategy involves pausing the game, and clicking the 'talk' button onto the enemy while they are still neutral. Then, while the game is still paused, force-attacking the creature with your party members. This means that while the creature is waiting for you to start talking, you are attacking, and probably carving it up into meaty chunks without it noticing. You will have to repeat this tactic every few seconds, as the creature will eventually realize that you are fighting it, and will go hostile.

Single Player- Importing items
When you start a new game with an imported character, for a few seconds (before the starting cut-scene) your imported character still has all his equipment. As soon as the game has finished loading, and you can see a black screen, pause the game. If necessary, press 'h' to reveal your menus. Open up your character inventory, and drop all the items that the character has. Unpause the game. After the cut-scene has finished, all of the items should still be on the ground. You can then re-equip them.
Note: You must press pause before you hear the groan from your character, that signals the start of the cut-scene, otherwise it won't work.