1. Sell music, not subscriptions. There is only one company that does this properly and it's called Apple. Subscriptions don't work. They're antithetical to the very idea of how you buy music. They don't work for low volume customers. Not everyone is a music addict - and the iTunes pricing enables a person to hear a song they like on the radio, type it in and buy the song. Impulse buys don't happen if you've got to commit to a $8 a month subscription, 
2. Sell real MP3s or something that is quite easy to turn in to an MP3. Apple does this reasonably well. Nobody else really does it very well. Apple has the biggest market in MP3 players. Make sure your stuff works on them. That means MP3. MP3 is device neutral, WMA, AAC and the multidue of DRM systems aren't.
3. Once a user has bought a track, make sure that the the user can go back and download extra copies. Hard drives fail, computers get stolen, shit happens. The users are buying intellectual property not download megabytes.
4. Offer podcast clearance rights for commercial music. Allow podcasters to register with your site and pay a chunk of extra cash to have the right to play it on a podcast, The royalty collection agencies are totally irrelevant in the podcast realm, so work around them. The one really valuable bit of PodShow is the Podsafe Music Network. If someone has got a song that cost them $1, let them pay 50 cents more to promote the music.
5. Offer an affiliate programme and build an API. Go and look up Amazon ECS. This is letting people use the data of Amazon's catalogue and sell stuff to their users.
6. Top up the albums. If I buy one or two songs on iTunes, I might want to top up and buy the rest of them. Take the album price, deduct from it the amount someone has paid for tracks from that album and then sell them the rest of the album for that amount. And no bloody 'Album Only' tracks. That's stupid.
7. If you have software, bug your users to backup their music to a DVD-R. Not just their purchased music but all their music. It's highly sensible, which is why I didn't do it.
8. If you are building hardware or software to play MP3s, remember that not all MP3s are music and not all MP3s are three minutes long. The iTunes and iPod experience has this knowledge built in. The Zune doesn't.
9. Cut the parental controls rubbish. Or at least make sure that the explicit version actually is and not vice versa (I've seen a rap album on iTunes with an explicit and clean version - only they've messed up and got the two confused).
10. Give the end user a reason to want to buy music, not a reason to not want to. DRM is the best reason not to buy music.
