I wrote an article for PocketGamer.biz which went up today. In it, I argue that the most important part of marketing your indie game is the design of your game itself. It's about designing your game to be marketable, and that for a game to be marketable it needs to be remarkable. Your game should encourage discussion, and it's up to you to create a dialogue around your game as early as possible.
Have a look, and I hope you find it useful!
Pocket Gamer: Greedy Bankers' Alistair Aitcheson on why indie marketing starts with game design