I just found great articles about being a great part-time freelancer.
Here the short list:

1. Keep Your Full-Time Job
2. Set Up a Basic Portfolio Site
3. Prioritize Experience Over Income
4. Work Your Own Projects
5. Establish a Basic Work Schedule
6. Open a Separate Bank Account
7. Re-Invest the Money that You Take
8. Don’t Forget About Taxes
9. Talk to People You Know
10. Visit Design Job Boards
11. Be Comfortable with Your Rates
12. Don’t Take Too Much Client Work
13. Network
14. Develop Your Own Business Practices
15. Plan for Differentiation

This article is intended primarily for those who have some experience with design but are looking to gain more experience and improve their skills before going into full-time freelancing.

Read for more detail here