There are 5 skills in Crackdown. Agility, Explosives, Driving, Firearms, and Strength

The maximum level for each skill is attained at the Four-Star rating. The player begins with a Zero-Star rating, essentially giving each skill 5 Levels in total; Zero-Star, One-Star, Two-star, Three-Star, and Four-star (being the maximum).

In order to increase your level in each skill, you must perform actions relating to each skill, that usually involve killing Gang members utilizing each respective skill.