The most important thing is DON'T SPAM. Also get your own domain name. Even if you just use it to redirect traffic your traffic to your myspace or soundclick or whatever page. Make sure to utilize the forums on the internet but don't spam. I would say that you shouldn't even ask for reviews of your music for at least your first few weeks on a site. Make sure you engage in dialogue with people and build relationships. This is key. Also make sure you build up an email mailing list. Give away free songs/beats and also give out tips or any beneficial info you can to your subscribers. Remember you can have the hottest music but if people don't like you then you're screwed. People will want to do business with you and help you if they like you, so BUILD YOUR RELATIONSHIPS and Promote, Promote, Promote!!!