There are many ways to control crab grass, non-herbicidal and herbicidal but the best way is to maintain a lawn with conditions unsuitable for crab grass growth i.e. a correctly fertilized, thick and well watered lawn. Existing crab grass can be pulled out with a hoe so that their roots dry out. Did you mean crab grass on your beds or lawn? If it is on your flower beds I have also heard that you can use a vinegar/liquid dish washing detergent mixture (1 gallon white vinegar and 8 drops of detergent) to kill the crab grass by spraying.
If your lawn isn't too big and you don't mind putting some work in yourself, you can pull it out by hand. If you are an organic gardener, vinegar seems to work well but be careful if you choose to use this.
