Any good plastic cleaner and a microfiber cloth will do the job just fine. For cameras and lens bodies, apply a small amount of the cleaner to the cloth and wipe the surfaces down. This will prevent it from getting into places where it shouldn't.

Many plastic cleaners leave behind a very thin layer that fills in microscopic surface irregularities (sorry, I know that reads like marketing copy), making it more resistant to smudges and easier to clean. Pretty much everything plastic I buy -- ranging from motorcycle fairings to musical instruments to some of my camera gear -- gets a couple of goings-over early in its life.

The two cleaners I recommend are Plexus Plastic Cleaner (which is what I've been using for the last decade or so) and Novus #1 Plastic Clean & Shine. Be aware that Novus has three formulas, and the other two contain light abrasives. They're both a little expensive, but a little goes a very long way. Both are available worldwide and can usually be found at shops catering to aviation, RVs or motorcycles or from some plastic supply houses.