"Sets" are refrences to street gangs. Set tripping is violent results from the confrontation of two rival gangs or gang members. Gang members identify eachother by tattoos, hand signs, and colors worn. Gang members or gangbangers rarley hesitate to attack another gang member who represents a rival gang.
"Ready to pop the clip in, ready to start (set) trippin'" - T.I.
We was in the club and this nigga' starts set tripping.