A dead battery can be a real pain in the but, especially if your bike doesn't have a kick starter. Sometimes you can push start your bike, but that's not ideal. There are several things you can do if your battery takes a dump on you. Here's a look at them.
Ari Henning of Motorcyclist Magazine goes over the things you should and shouldn't do if your bike's battery doesn't have enough juice to get your engine started. He makes some great points, and it's something you're probably going to have to deal with at some point so you may want to listen up.
So, let's recap. If you're bike has a dead battery, and your not in a hurry, you can hook it up to a battery charger and come back later.
The second option is to have someone jump start your bike, just like you would do if your car battery were to die. The car's extra electrical power won't fry any of your bike's electronics.
Your third option is to use a jumper box that can be used as a portable jump starter. The guys at the MC Garage recommend the Deltran Portable Power Pack. I've linked to it below.
Here's links to Amazon for the gear he talks about in the video: