1) Water it in the morning because the sun will help dry it. You don't want to do it at night because without the sun, the water will just saturate and not dry. We all know what too much moisture can do, fungus, etc.
2) Pull weeds whenever the pop-up. You can also you preventitive chemicals early in the spring.
3) Reseed wherever necessary, the fall is the best time for cool season gras and late srping for warm season grass.
4) Mow the lawn on a regular basis and don't cut it too short. It's recommended never cut-off more then a third of the blade.
5) The lawn needs to eat! Food is essential so make sure you feed it on a reular basis. There are many types of fertilizers out there so inquire about which will work best for you. keep in my dormant grass can't take nutrients so avoid feeding it.