You may want a ceiling installed in your garage. A garage ceiling can improve the appearance of your garage, and if it is painted white it can help to reflect light down into the garage area and improve visibility. If you insulate the ceiling before finishing it, you can also increase the heat efficiency of your garage.
The easiest way to finish your garage ceiling, and one that is not expensive, is to install drywall on the undersides of the ceiling rafters. For a garage application, you can either leave the drywall in its raw state or you can tape and spackle the joints and finish the ceiling with a coat of flat white paint. Having a helper to install drywall makes it much easier, particularly when you are working overhead. You can buy drywall in sheets that are 4 feet wide and 8, 10 or 12 feet long. The larger the sheets, the more difficult they are to work with, but the fewer joints you will have to finish.
Lowered ceilings are an excellent solution for overhead areas that have a lot of pipes or vents that would get in the way of conventional drywalling. A lowered ceiling consists of a grid of aluminum "T"channels suspended from the ceiling with wires. Foam or cardboard squares are placed in the spaces created by the channels, making a solid ceiling that covers up everything above it. Lowered ceilings are an inexpensive choice for a garage, particularly if you buy the materials at a home improvement store and do the work yourself.
If you have more time than money, you can finish your garage ceiling virtually for free by salvaging used planks of wood and applying them to the underside of the rafters. If you live in a rural area, you may be able to find a farmer or landowner with a derelict barn who is willing to give you the materials in exchange for you disassembling it. A barn board garage ceiling would be an unusual conversation piece for your home.
The cheapest form of garage ceiling is one that is left with bare rafters and nothing underneath them. This leaves the garage with a somewhat unfinished look, but if you aren't fussy about the aesthetics of your garage, it shouldn't be a problem. An advantage of this method is that you can apply strips of wood to the underside of the rafters and use the spaces between the rafters for storage.