MySpace used to be the social network site that every musician needed to be on, but now MySpace is considered "past it" you're better off focussing on Facebook. While Facebook is not a site people tend to browse to discover new music, it's a good way to give yourself a presence in the online life of a potential fan if you can get them to click that all-important "like" button.
Here are my top 5 tips for turning visits into likes:
1. Keep it simple - don't clutter your page with loads of tabs.
2. If you want a music tab, choose either Soundcloud or YouTube. These are familiar to most users and you won't have to upload your songs twice or have your view/play counts split across different sites.
3. Put all the important info you want people to know on your info page. If you have any impressive achievements (e.g. press coverage, festival appearances) don't forget include them, but don't make the "about" section too long or no-one will read it.
4. Include at least one clear photo of yourself or your band. It's hard to become a fan of an act if you've got no idea who they are.
5. Keep the page regularly updated. If you leave big gaps between updates people will think you're not busy. Links to music videos you like are always good filler posts as it keeps the focus on music and shows what your influences are.