I'll tell you what I tell most people starting off:
- Figure out how much money you think your art is worth. Look around at other artists' prices, think about how much you need/want to make, etc. Even if you're doing "name your price" commissions, you figure out some kind of standard for what kind of art you'll give for what kind of money you're getting.
- Advertise. Post on furry forums, post journals/notes on DA or FA, ask your friends to advertise for you too... whatever you can do to get the word out.
- Draw a lot. Do personal art or practice drawings to improve your skills. The more art you submit to art sites like FA, the more people will see your work, and the greater chance someone will come along who wants something from you.
- Get commissions done quickly, and stay on top of communicating with your clients. Clients can often come back for another drawing if they like working with you; if they have a bad experience, they won't return and could also tell other people to stay away from you.