there is tons of information on a forum site called mernetwork: http://mernetwork.com/index/forum.php
also, you can buy tails. anything ranging from inexpensive fabric (bathing suit material) tails, all the way up to $3,000+ full silicone EXTREMELY realistic tails. most beginners should start off with either a simple fabric tail or a partial silicone tail (which means it's made with neoprene and silicone, still looks realistic as full silicone, but isn't as expensive or heavy, but these kinds of tails should only be bought if you're finished growing, since they are about $500 - $1,000, depending on the tailmaker).
on mernetwork, there are tutorials on how to make your own tails, whether you're looking to make a fabric, neoprene, partial silicone, or full silicone tail. there are also links to tailmakers and reviews by people who have bought from them and used the tails. some are good, some aren't, but it's easier to get an idea of who is more reliable and whose products tend to be more durable.
i'll post a few links to tailmakers' pages:
- merbella studios (partial silicone & full silicone, as well as tops and accessories): https://www.facebook.com/MerBellaStudios
- fish butts (partial silicone & full silicone): https://www.facebook.com/fishbuttsforsale?fref=ts
- the mertailor (fabric, partial silicone, full silicone, tops & accessories): http://www.themertailor.com/
- aquatails (fabric, neoprene, dry tails, tops & accessories, especially good for the younger merfolk): http://www.aquatails.com/
- magictails (fabric, comes with a matching top): http://www.magictail.de/
- mermagica (fabric, tops & accessories): http://www.mermagica.com/
and those aren't even half of the tailmakers. i personally have a tail from fish butts (an older one, before she started working with silicone, so mine is latex), and i love it. here is a link to the tailmaker reviews page on mernetwork: http://mernetwork.com/index/forumdisplay.php?74-Tailmaker-Reviews
more people need to see this and figure out that spells and potions WILL NOT CHANGE YOU INTO A MERMAID.
i hope this helps everyone :D
~ Mermaid Annariea
mernetwork & about 4 years of mermaiding research.