You can use tags to find all of my ramblings on sculpties, but it's kind of word soup in there. So here's an attempt at a handy dandy guide of what's where.
Step by step...badly. Sort of. Tips with no shiny pictures, because I am lazy:
Getting Started: A very quick and dirty crash course in how to get up and running. Use a premapped sphere, and jump straight in to using the modeling tools (the fun part!). This is to get your familiar enough to hit the ground running, it doesn't teach you how to master Blender. Because Blender is evil and complicated, and I don't know how to do most things in it.
UV mapping the hard way: Say you didn't use that premapped sphere to start out with, and in fact, did your sculpting first, and then decided you needed to map it. It ain't pretty, unless you go through a number of seemingly extraneous steps. If you do this, it is imperative you preview your sculpts before uploading, as getting them backwards is really easy.
Texturing sculpts: some quick and dirty tips to get your started in the world of texturing with Blender. Does not include advanced techniques, but at least gets you pointed in a vaguely decent direction to start.
Texturing and the Avatar mesh: how to import the av mesh into Blender, and a few things to do from there, as well as how to be able to paint on a sculpt to line up better with an avatar clothing texture (note: your mileage may vary, since we don't get to play with the real av mesh, just a vague approximation).
Importing Sculpt Maps to Blender: we've covered how to make an object in Blender into a sculpty. But what about taking one of those rainbow maps and making it into an object in Blender we can play with? Here's how.
Awesome things that make life easier:
Link to a pre mapped sphere: Find mapping a pain in the ass? You're in luck! Here, have a sphere to start with that's already had all that crap done to it. You just need to rebake when you've finished your sculpting.
SLImageUploader: example of mush to awesome with SLImageUpload. Also, if you're having some side seam distortion, this should fix it, because it doesn't use the stupid JPEG compression...which is idiotic when we're talking something where every pixel does matter. Yes, even when you tick lossless in the SL client, it lies like a filthy whore.
Extra tips for other problems:
Mirroring: a very brief couple of tips about what to do if you find your sculpt map is inside out in SL. This is why you pretty much always want to preview the sculpt in SL, even if you're then logging out to use SLImageUploader.
Sculpt Mapping: an overview of the different mapping modes you can set for your sculpt in SL. Generally you'll go with the default sphere, but the others do have their uses.
Sizing Sculpties Smaller: Say you need miniprim sculpties for something. Sculpts only natively go down so far, and there's no dimpling to save you. However, adjusting the map in Photoshop can shrink them down nicely.