Visit this page for direct links to online check-in.
Checking online is quick and easy. You can do so 24 hours prior to your departure while you're at work or at home. After completing your online check-in online, you can print your boarding pass at the airport using a self service check in kiosk, or choose to receive an electronic boarding pass directly to your mobile device. The benefits of online check-in are:
a) Check in 24 hours before departure
b) No need to wait in line for an airport agent
c) Print your own boarding card
d) Quick and easy to do, no need to leave the house