I used butcher paper (it was free from my mom's work) and the paper was so thick I couldn't put pins through it (also the fabric decided to not want to be pinned also which proved problematic throughout the process) so I had to devise my own pattern weights (coasters haha). I took my friend's measurements and did a few doodles and viola! a pattern emerged!
It came to 4 pieces; the front and back of the skirt, the fin (a circle skirt), and the top fin. We found really awesome fish scale fabric at Jo-Ann's and used that for the skirt (it didn't like being pinned) and a pretty stretchy lime sparkly fabric for the fin.
I had to do some minor adjustments after a fitting but nothing too big. I think the final product turned out great. Now I have a pattern for an awesome mermaid skirt for the future!