"When you finish the encounter, you receive a mission to extort money for Winston. Going after Jack you get to the first marked shop. Press triangle and collect money.
At the third and fourth stalls you'll have a fight with groups of thugs.
Defeat them, take the payment and go to the clothes shop. Choosing items from the same set, you get a small bonus to statistics.
After the change, run at the marked direction and the mission ends. You receive experience points in two categories: "Cop" and "Triad". To increase first one, you have to obey the law: do not attack pedestrians, destroy other's things and try to behave rather well. To increase the second one, you have to fight attractively and be very brutal. Points are showing at every meaningful behavior. When you fill the bar of the category, you level up and get new upgrades to choose.