Each diversion has 3 tiers of stars, Bronze, Silver, and Gold. Each tier has three stars.
The Statistics page lists the total number of Bronze, Silver and Gold stars earned, the maximum amount of Gold stars possible to earn in the game is 72.
In the Diversions menu, each Diversion rated by stars is listed, along with the highest star level earned, the total number of stars earned, and the total amount of respect earned through that diversion.
This is a full list of all Diversions which are rated with stars.
Gang Kills and Headshots - best done with Shock Paddles by reviving and killing a gang member.
Shield Kills - best done during Drive-by Diversion, especially at level 7 (4th group), where there are 14 members in total or during FUZZ by entering the Saints Hideout and killing Saints gang members.
Two Wheels - best done by towing a front or a rear cab of the El Train with a Shaft and going forward or backward.
Vehicle Surfing - best done on the freeway or in Co-op.
Windshield Cannon - best done by glitching through the map using any fast vehicle and driving towards the gas station at high speed. On rare occasions the vehicle may stuck in textures and Playa may glitch through the map.