I'd be happy to explain.
I use Z-Brush almost exclusively, with an occasional overall size measurement in netfabb. Basically I pick a cool sounding creature/cryptid from Wikipedia or any of the numerous sources on the internet (or books), read about its physical description, look up images of it, and decide what real animal it's most like. In many cases, it's a combination of real animals, or humans. I then do a Google search for the different bones of the animal they're most like, (I've been doing this less as I learn what everything looks like and build up a library of pre-sculpted bones).
Then I put on some music (If I remember to - So many times I put in my earbuds, and get so focused on what I'm sculpting that I forget to turn the music on) and I sculpt. I start from a sphere for any new parts, and treat it like I would normal clay. Any parts I've already made, I import and adjust to fit the skeleton. The more I sculpt, the more reusable pieces I end up with, and the less I need to do from scratch on new pieces. I basically ignore poly/shell count until the end, since it's not really important when printing. Unlike a lot of people on here, I never focused on modeling with low poly counts, since I've been modeling for print since I started.
When I'm done modeling, I use the Decimation Master in Z-Brush to get the models under 1mil polys (I aim for 400k to 700k, to keep upload times down), then use the Print Exporter to get it as a correctly sized .obj. I upload it, see any problem areas in the wall thickness checker (So much better than netfabb), tweak it and upload it again until no problems are shown. Usually takes 1-3 re-uploads, sometimes none, as I can sort of tell if a part is too thin at this point.
And that pretty sums it up.
Also, It's Brian with an "i".