A lot of photographers swear by Eclipse. Don't get the cheap cleaners, because they will leave a residue on the lens after they dry. What I do is get a microfibre cloth, one of those nifty ones that also doubles as a gray card, and breathe on the lens and wipe it. Gets it crystal clear every single time. And don't worry too much about putting a little force into your wipes; a lot of people have this idea that lens coatings are *so* fragile but they're really quite robust, and are baked onto the glass during production. Just make sure when you wipe that the cloth doesn't have any grit on it.