For internet based battles---
it's all about promoting shamelessly through facebook, twitter, tumblr, youtube...
do you frequent many message boards? post on there!
Have a big family? it might be time to make that call to your grandparents that you've been putting off. tell ALL of your relatives... even that cousin that hangs out in the corner picking his nose at family get togethers.
Make an event page on facebook! invite all your friends! (there is a code to select all your friends, google it, it will save your clicking finger.)
When you hang out with your friends, tell them about it! have them hang out at your place, and when they do, make them vote if they havent yet, log into facebook and invite all of your friends friends using the same code!
Street team... go out to your local hangouts and hand out hundreds of burned demos with a link to the poll written on the sleeve.
I just won Buffalo's biggest battle of the bands and our band walked away with 5000 bucks! These methods really do work. The contest we were in went on for over 7 months... this band vs this band, etc... getting one band each week, then a live quarter final... multiplied by four to get the 4 final bands squaring off at the final live round... winners based on voter turnout.
if you really want to win, make it a priority. devote ALL of your free time to promoting this contest and your band.