Tooltips are notoriously difficult to handle in WoW UI code, as the interaction of GameTooltip methods can be quite complicated. This page has some examples for the use of tooltips, and a collection of advanced points to note about the finer details. For an indepth analysis of GameTooltip methods, see Tooltip Pseudo Code for a Lua-ish pseudo code representation of every GameTooltip method. See Widget API for a reference list of all GameTooltip methods.