On a regular basis, look at the entire chain by standing to the side of your bike and lifting the rear wheel off the ground. Use your free hand to slowly rotate the closest pedal, inspecting individual chain links for dirt buildup, rust and/or tight links (links that do not bend easily as they pass through the rear derailleur). Also check for adequate lubrication by listening for squeaks while riding. If you find any of these condition, your chain needs at least a spot-cleaning.