Started topping my boyfriend after years of mostly sub. The trick was to 1) find out what sort of things he wanted done to him and then 2) buy a lot of tools. Stockroom.com
, Amazon, Babeland, Good Vibrations - they all have good options. Also, work up to intense sensations slowly so you know your sub's limits, and don't hit along the spine. And beware cheap nipple clamps because them things can be *dangerous*.