The single most important—and neglected—parts of a bicycle are its gears. When people look to buy a new bicycle, they often look at the frame and the wheels, maybe squeeze the brakes, but rarely do they inquire into the quality of the gears. What's more, most people don't make proper use of the gears they have. I've seen far too many people on old bicycles that would function fine were it not for the rusted, useless gears that slow them down and hurt their knees. Not only that, but I also often see people riding uphill in their hardest gear, or simply riding with their chain crossed to the point that it is rubbing on the derailleur. Fortunately all these issues—buying the right gears, maintaining your gears and riding in a good gear—are incredibly easy to remedy.