Clean and lube the chain; the shop will take care of the rest
Simple yet sophisticated, the bicycle chain is arguably the world's most efficient and reliable propulsion device -- when you take care of it, that is. Here's how:
When you apply lube, let it sit a bit and then wipe off the excess. You don't want excess oil on your chain because it picks up dirt (which makes things wear faster) and increases the amount of grime that builds up on your sprockets and shifters. A messy chain marks you with hard-to-remove grease tattoos anytime you get near it, and it'll do the same to your car if you transport your bike in it.