According to this LSU AGcenter post, which can be found here…
http://www.lsuagcenter.com/articles/page1517323246000
the best way to deal with crabgrass is to start now. You have to get out in front of it in order to have any meaningful control. In a nutshell using a pre-emergent herbicide labeled for crabgrass control should do the trick. But you have to apply the product according to instructions. Just be advised that if following the prescribed rate gives you good control applying more or more often does not give you better control. Also, rarely are herbicides one shot applications, very often you will have to reapply. So follow the directions and you should get reasonable control. If you read the post you can get a good of idea as how to start your crabgrass control program.
After reading the LSU post I dug up a little info on crabgrass. I bet you didn’t know, I sure didn’t, that crabgrass was introduced in 1894 into the U.S. by the U.S. patent office as a forage crop. Thank you U.S. government. Crabgrass is also a native to Europe or Eurasia but now is found worldwide and in virtually every crop and crop situation. The reason that it is best to start you crabgrass control now is because the seeds need 4 to 5 consecutive days of soil surface temps to be at 55 or above. We start to see favorable conditions in south Louisiana around mid February. Unfortunately crabgrass is a very prolific seed producer and can take several seasons to get under control. As with most turfgrass weeds, cultural control is the best method for controlling and preventing a re-infestation. So keep your grass cut the the appropriate length. Cut it on a regular basis, according the season. Water when it needs it and maintain an appropriate nutritional program. A good healthy lawn best herbicide.