Skill Tricks are minor adjustments or abilities to existing skills.
Skill tricks are special maneuvers, so you can't just use them as often as you want. Unless otherwise noted, a skill trick can be performed only once per encounter (or once per minute, for scenes that don't involve combat or other conflict). This restriction sets skill tricks apart from feats and class features, which are often repeatable.
Typically, performing a skill trick is either part of another action or an action in itself. Each skill trick's description specifies what sort of action, if any, is required.
A skill trick usually either requires a successful skill check to pull off, or it 'piggybacks' on a skill check you're already making. For example, the Extreme Leap trick functions only if you've already succeeded on a DC 20 Jump check (or DC 10 with a running start) to make a horizontal jump; it doesn't require a separate Jump check. Exceptions to this general rule are noted in the skill trick descriptions.
Using a skill trick does not provoke attacks of opportunity unless its description specifically states that it does (or it involves an action that would normally provoke attacks of opportunity, such as moving our of a threatened square).
List of Skill Tricks: This list is based on the 3.5 skill system though. Since we're using Pathfinder, the skill requirements for any one trick are reduced by -3. There may be other lists. Swade?