Your description can be important to finding a suspect. But often eye witness accounts are inaccurate because we are concentrating on our cell phone, reading a book, thinking about our job, etc. and not paying attention to what is going on around us. As you walk around in your neighborhood, in town or at the mall, get in the habit of looking around you.
In the case that you witness a crime, focus on one or two items of a person such as their sex, height, weight, race, physical impairments, or approximate age. Often descriptions of shoes are good because even if a suspect changes their clothes they may not change their shoes.
Vehicle descriptions are always important to finding suspects. Try to concentrate on the license number to report to 911. Even a partial plate number can help deputies. Make and model of a vehicle as well as whether it is a sedan, two door, four door, truck, SUV, and its color are also helpful.
Report what you see to 911 immediately. You will forget what you saw as time goes by. It’s a good idea to keep a small notebook to write down what you saw. You can also use your notebook for your to do's, and notes for your everyday tasks.
The video below shows how hard it can be to give a good description and some hints on how to be an effective witness.