Dex 13, Dodge.
You get a +4 dodge bonus to Armor Class against attacks of opportunity caused when you move out of or within a threatened area. A condition that makes you lose your Dexterity bonus to Armor Class (if any) also makes you lose dodge bonuses.
Dodge bonuses stack with each other, unlike most types of bonuses.
A fighter may select Mobility as one of his fighter bonus feats.