WD-40 is good for removing grease and oils. But it does NOT provide lubrication. It evaporates rapidly, after removing what was left by way of lubrication. Such as bicycle-grease or similar products such as marine-grease for boating. You want to get real grease and use real good oil where lubrication is needed. For instance: Oil the pivots on your derailleurs. Grease the hubs and bottom-bracket.

Here's a good lesson on the use of WD-40 and bikes:

http://bicycletutor.com/no-wd40-bike-chain/