Study the rules A LOT. Form opinions on what those rules mean.
Get on Zebra Huddle, be willing to accept that your opinions were wrong.
Travel as much as possible, see a lot of derby.
Be willing to do any job.
If you want to be good be ready to travel.
Know your weaknesses, if you're asked to ref a bout give an honest representation of your skills.
My advice is to push complete and unemotional attachment from home leagues to refs. The quicker they can let go of that, the more they can focus on reffing (and believe me it took guest reffing for other leagues almost once a month to realize that.) I am not sure if that helps, but it worked for me.
yes, study the rules. but do not just learn the words. reffing is providing the platform on which the girls can compete. yes, get on ZebraHuddle.com I am learning a lot there every time I visit. try reffing as often and with different leagues/refs as you can. I wish I had more opportunities here...