I used labor statistics to determine my rates. The Department of Labor has very useful statistics and they are broken down by state. You can get the information nicely broken down for you at
http://www.careeronestop.org/
They also have information that can help you describe what you do. Another good site is
http://www.onetonline.org/ which has extensive descriptions of jobs and their duties as well as knowledge and education needed.
I also used my state's statistics. I'm in Vermont and they have the statistics broken down per region so that in quoting to local folks I have a rationale for my charges. You will probably easily find those statistics by going to your state's Department of Labor site.
The second figure I used, from the U.S. Department of Labor was the average compensation cost (such as insurance, taxes, etc.) The current national figure for that can be found at:
http://www.bls.gov/news.release/pdf/ecec.pdf
In determining packages I just used a percentage discount--10% for 10 hours and 20% for 20 hours.
One caveat: I am also new to this and so don't know how my reasoning will work out.
We'll see.
Best of luck to all of us!
Leanne