My last two main guitars have been maple, and I've been able to keep them clean just by washing my hands before I play and wiping them with a dry cloth afterwards. I clean every time I change strings. I used to use a very lightly damp cloth.

For the last several months, I've been using the Ernie Ball Wonder Wipes, which I really like, but they're only for unfinished maple or rosewood, not for finished maple like you have on a Strat. They're great if you've got an old rosewood board that's getting a bit dry, too. It's essentially the lemon oil treatment in a pop-up wipe.