Here is some good advice I received from Jay Henderson of Hollywood Cycles. Keeping your shifting mechanism clean is, I'm guessing something you never think about. All it takes is a few minutes and is so simple. Pull back your hoods on your brakes, tip the bike upside down and use a few Q-tips between all the moving parts to maintaining good shifting. Jay says the cheaper Q-tips work better than the brand name because they are more likely not to leave behind any cotton. Additionally, it's a good idea to occasionally clean the cable guides under your bottom bracket. Warm, soapy water will take care of the sticky residue that can be left from your water bottles.