I think it's important to keep an open development cycle in mind. The earlier on in a project that you start talking about it, the more time you have to gain attention and traction from press. It also gets people hyped for your game, and even tell their friends about it. It's difficult to build up groundswell right at the end of development, because it takes time to accumulate. That's definitely something that we learned on our last project, and are hoping to change on our next game.
It's important to recognize that the strongest marketing comes from telling people who really care about your games, and the best way to do that is to tell fans. Building a fan base takes a long time though, which again is why you need to start early on. You have to focus on the long game and recognize that your first game might not sell very well. For us at NAHCS, we decided to make our first few games free to build our name and our fan base, so that we can establish ourselves better. Time will tell how that works out, but that's about all I have to say on the topic for now haha.
Co-founder and Primary Developer at [URL="http://www.nahcsgames.com"]NAHCSgames.com[/URL].
Check out our first game [URL="http://bitly.com/1dDrDqi"]#REALBIRD_REAL[/URL], a free download on the iTunes App Store.