Springs if you don't have a lot of cash. Springs and camber kits if you have a little more cash, and don't want to wear your tires out, or coilovers if you have even more cash and want a better suspention upgrade all around. I'm currently lowered on Skunk 2 springs, with a Skunk rear camber kit, and Ingalls front camber bolts.
Lowering springs will cause your dampers (shocks) to blow sooner than a stock spring would. How soon, that depends on the amount of drop, spring rate, roads and driving style. So, if you get springs, start saving for dampers.