I use something called Metal Protector (very similar to WD-40). Nice thing about this stuff is that it leaves a dry lubricate behind, and it does not hurt paint, fabric, rubber and plastic. Like WD-40 it cleans the bike very nicely. I even use it on the exhaust, but only if I don't plan on riding until the next day.

Tom

Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety. Benjamin Franklin, US author, diplomat, inventor, physicist, politician, & printer (1706 - 1790)