Myspace is a site most teens with a profile use EVERYDAY so why not take advantage of this. If you have a profile with many friends then you are already half way there. If you do not the first step is to create a myspace page. Make the page HUMAN. Do not make it seem as if you are not a person. If people think you are not a person then you will not get as many referrals. Pick what you will be trying to get people to sign up for and have a referral link about that on your page but do not bombard them with banners and links. Once you have your page setup, start making friends. Target friends you think will want to do what you are advertising. Think about this more as letting people know of a great opportunity. Make friends who will want take advantage of the opportunity you are telling them about.
So for instance a great site to advertise is Shared Reviews. It is a good site that people are going to want to do and they have a great referal program. The only thing you have to do is let people know about the site. Do not try to convince them to sign up. Just tell them of the sucess you have had with this program. There is no reason to try to convince them to sign up. The site convinves people it self.
So once you have your site, and your idea and you are in the midst of adding friends, just start writing on your blog about the site. Also you can send out a buliten for people to check out a program. Again don't make it sound like one of those stupid offers no one uses. Just use the site normally. Comment your friends site so they will look at your site. DON"T SPAM. Just use the site for fun while at the same time letting people know about the website you are promoting.
A great program to use if you are willing to spend some money is Open Adder. You can get a free trial at openadder.com. This site allows you to add friends, send comments, message and bulitens all automated. This will save you hours of time but you dont need it.