It depends on what you want them to do...there are tabs to assist the pilot, tabs to oppose the pilot, tabs to trim, tabs for the pilot to alter the trim...moving tabs and fixed tabs. There are tabs the pilot moves, tabs that move because the surface it's attached to moves, tabs that don't, and tabs that only move after a specific load is applied to the surface it's attached to...but they boil down to three distinct types, those that assist surface movement, those that oppose surface movement, and those that bias the whole surface circuit.
Evan, WB #12.