While taking your shoes into a professional cleaner is one option, a more sensible (and economic) alternative may be to clean them yourself using a home remedy.
Machine Wash
Most tennis shoes are machine washable. If, however, your tennis shoes have leather or suede on them, then avoid machine washing them. Otherwise, remove the laces and insoles. Pre-treat any obvious stains by rubbing laundry detergent directly on the stained area. Throw the shoes into the machine and set the temperature to cold. Air dry the shoes when you're finished. If you have suede shoes, you can rub the stains out with a dry toothbrush or by applying a suede shampoo to the stains. Do not get suede shoes wet. To clean leather shoes, apply leather shoe polish to the stains and buff them out with a shoe brush.
Stain Removal Pens
Stain removal pens are products that can be applied directly to stains for powerful and accurate spot cleaning. These are portable magic marker-sized devices that contain stain removing solutions inside. You simply press the pen to the stain and then the solution is released. Rub the stain out with the marker tip, and then rinse clean with cold water when you're done. Stain removal pens such as Tide To Go, the Zap Stain Remover Pen and the Magic Wand Stain Remover Stick can be purchased online or in retail stores.
Shaving Cream
According to Jack Cassimatis, author of "The Super Stain Remover Book," shaving cream can actually be used to clean tennis shoes. There are two ways to use shaving cream for this purpose. One way is to coat your shoes in the cream, and let them sit until the cream has completely dried. Then, scrub the cream off with a soft bristle toothbrush or shoe brush. The second way is to coat your shoes in shaving cream, then wipe away the cream with a damp rag immediately. Let them air dry either way.
Homemade Cleaning Solution
Fill a sink or bucket with one-eighth of a cup of dish soap, a quarter cup of washing soda, a quarter cup of borax and a couple gallons of water. Stir the solution until it's well mixed. Add the shoes to the bucket or sink, and allow them to soak for a couple hours. You may have to put an object on time of them to make sure they stay submerged. Remove them from the bucket and then scrub them with a scrub brush. Rinse them clean with cold water.