Chances are you probably won't have too many friends and neighbors volunteering to take care of your lawn while you're gone, here's a few things you can do to ensure it will still be there when you get back.
Mow your lawn just before you leave. It might be a good idea to lower the height a little bit so it's not too shaggy when you get back. Be careful not to lower the height too much and scalp the grass.
Water heavily after mowing. If you don't have automatic sprinklers, try to give the lawn a good soaking before you leave to prevent browning out while you're gone.
Spot spray weeds. Any weeds that are there before you leave, will be bigger and uglier when you get back. Spot spraying with a selective herbicide before you leave will spare you a weed infested jungle upon returning from your trip.
Don't fertilize before you leave. A flush of growth is not what you want to be happening to your lawn while your gone.
Don't aerate, de-thatch or perform any other major cultural practices to your lawn right before leaving. The period immediately following these activities is an important time to monitor plant health and be on the look-out for stress induced decline.
