If you are not averse to chemicals, you can put down a pre-emergent between forsythia and lilac bloom. Most of the pre-emergents come with fertilizer, but you can find "contractor's" pre-emergent that does not contain fertilizer and is much less expensive than the highly advertised brands.

Set the mower blade high as this helps shade out crabgrass.

Here is Rutgers Cooperative Extension's fact sheet on crabgrass. You have to download it but it's free. This is the information you would receive if you contacted your local extension center.

Here is a link that might be useful: RCRE factsheet on crabgrass