You can balance some fans simply by removing two of the adjacent blades and switching places with them. Mark them so you know which ones you replaced and if it helps, then do the same to the other two blades. Most of the time though, it's loose screws or the screw plate for the blade isn't making good contact with the motor housing. All the other suggestions will work too. Balancing can be time consuming but worth the effort, especially if the wobbly fan is over the bed.