I can not speak from personal experience yet, but i have read some tipps, which make really sence to me.
You need to build up a fan base of minimum 1000 people. They need to be or become real fans.
Create a website for you or your band and offer some free stuff for download (songs, desktop-pictures, apps, etc). Also make sure, people can buy your music and other merchandise stuff from your website. You can use sites like itunes. Allow your fans to buy single songs and not just whole albums. People might spend 1$ for a single song, while they maybe won't pay a higher price for a whole album, especially if they do not like all songs on it.
For merchandise stuff, offer t-shirts, mousepads, notebook & mobile phone covers, etc with your bands logo and lots of other things, be creative.
There are lots of sites online, that will produce those goods for you. You just need to upload your logo, set a price and earn a small percentage while the biggest part is earned by the company, but you do not have a costs for the production and don't have to care about sending the bought items to your fans, as the company does it all for you.
Have a little signup form to your newsletter for your fans, so they can sign up to get informed about your net gig, your next album and everything else about you or your band. Don't spam your fans with useless emails, but send them information or photos which are special and are not available in the public. That makes your fans feel special, treat your fans like friends.
Use the major social networks and link them all from and to your own website, to reach a bigger audience.
If you play live, offer your cds for sale at the concernt/liveact. You can sell "special editions" on your concert/liveact, which also include a t-shirt, or a cd with your autograph, or a band poster or any other additional gift, which your fans would think is cool to have. You also might think about selling branded (your band logo again) usb-sticks with your music, concert-photos, band-videos and more on it. I say it again, be creative, there is always something people will like and buy, especially if they are real fans .
If you don't want to sell usb sticks, you can sell dvds instead of cds and include pictures and videos on there as a dvd has plenty of space for data.
While your music can easily be copied, since everythings becomes digital, a t-shirt or any other physical goods can't be copied with a computer, so you can earn some additional money here.
Be creative, there's much more you can do to increase your income.
They most important part might be to give away some stuff for free, especially if you do not have many fans yet and need promotion to get know. Free stuff spreads fast if it is good
Hope there were some helpful and inspiring tipps for you.