The volunteers at DIY bike shop Bikerowave in Mar Vista won't fix your bike for you. They'll tell you exactly how to grease those wheel bearings and repair that punctured tube, and they'll ride along with you for each twist and turn, but your hands will be the ones getting dirty. Along the way, you'll say “please,” “thank you” and “excuse me” to pretty much everyone else in the crowded shop — not because you were told to, but just because it feels right. Bikerowave is also a great place to buy an inexpensive helmet and lights. You should always wear the former (seriously), and the latter are going to get stolen anyway, so why not get a deal? 12255 Venice Blvd., Mar Vista; (310) 230-5236, bikerowave.org.