Use the following trick when on a quest to find an item, either in a crate or as buried treasure. For buried treasure, find a safe spot to dig treasure. After digging, stay in the same location and the treasure will respawn. Continue doing this until you get a message stating "Nothing of interest found". At this point, you can no longer dig. For crates, do the same thing, but you may have to go back and forth between two crates for it to work.
Go to a house or building where there are guards. After killing the person, stand in a corner off to the side and wait for them to respawn. When they respawn and if they do not attack immediately, you can remain still, heal yourself, and voodoo.
Go to Misty Mire in Tortuga and attack the giant crabs, big alligators, and huge alligators using only grenades. They will not strike back.