You need to use herbicides to get rid of any existing crabgrass. Make sure you get an approved and recommended herbicide which does not cause damage to surrounding grass or plants. You also need to go through the label carefully to look for any chemicals or components that may be hazardous to health.
Apply herbicides according to season
This is extremely important. You can either use pre-emergent herbicides or post-emergent herbicides. There is a time for every herbicide and a corresponding effect. You must apply pre-emergent herbicides in early spring or late winter, as they will prevent any seeds from sprouting and will stop the crabgrass from growing. Similarly, apply post-emergent herbicides in late spring or early winter to kill the existing crabgrass growth.
Cut the crabgrass
After treating with herbicides, you should cut the crabgrass. This can be done with the help of a long scissor. Make sure you re-seed your garden in time for the next season after removing the crabgrass.
Hand weed the light infestations
If there are light infestations, you can remove them by hand. Gather the whole set of crabgrass in your hand and slowly pull the whole bunch out.