I'd agree that content really matters. I wouldn't try to overload on keywords, although if you can have something that reads smoothly while still hitting keyword density of around 2% then that's good. But the flow of traffic will depend a lot upon making your site something that people actually stay on for long enough to read it.
A well-written, fairly lengthy article (around 2k words is pretty much perfect) on the main page is good. It looks serious and gives a good impression, makes people more likely to stick around. Not placing too many ads, and placing them in the best spots will help too.