This campaign will be using Called Shots rules. They are as follows:
A called shot is an attack aimed at a particular part of the body, in the hope of gaining some extra effect from the attack. The smaller or better guarded the area, the more difficult the called shot. A called shot is a single attack made as a full-round action, and thus can’t be combined with a charge, feats like Vital Strike, or multiple attacks with a full-attack action.
Called shots are divided into three basic difficulty groups: easy, tricky, and challenging. Easy called shots represent large areas of the body, and are made at a –2 penalty. They have relatively minor effects unless a critical hit is scored or massive damage is dealt. Tricky called shots represent either smaller areas, like a hand, or areas a creature protects well, like its head. Tricky shots receive a –5 penalty, and inflict more serious consequences. Challenging called shots represent very small areas like eyes, fingers, or creatures’ necks. They receive a –10 penalty, and successful hits cause significant short-term impairment. Beyond these challenging ratings lie almost impossible called shots that receive a –20 penalty. For called shots against non-humanoid creatures, use common sense and the categories above as guidelines. For example, a flying creature’s wings are treated as arms. As always, this is up to GM discretion.
Please see this link for each of the successful Called Shots effects. Please read the content of teh page carefully in the event that you would like to use a Called Shot.