Pretty much, walk/run from one gig to the next but keep an ear out for gunfire and an eye out for flashing police markers on the mini map. You get some of that in a car, but its not as clear, a bike is probably better, but feet are best.so explore the city while enjoying the views and at the same time kill?
Also use the scanner frequently and you will find many groups of gangsters on corners, in parking lots and alleyways, some up to no good, some just minding their own business, but pretty much all with bounties and most with weapons. Provided you are careful not to endanger the civilians you should be able to take them out without too much police attention.