I'm ultimately just as much an amateur as you are, but a couple of things I've found:

Get the anatomy down first! That'll be the basis of anything you do well, even if it's the cartooniest thing imaginable. Look up Andrew Loomis and you'll find some great PDFs on human anatomy, proportions, etc. Public domain, too. ^_^ As for aminal anatomy (The stuff everyone needs to know, not the genitalia), I don't really have a holy-grail gold standard, but there's several groups on DA dedicated to that sort of thing. You might try there. On top of that, a good way to practice them is to find said animal on an image search and draw what you see, not anthro-fied or anything.

Don't hand-trace, eye-trace or try to learn every little thing from another artist's work, though. If you're good on anatomy and fundamentals you can get some ideas and tricks this way, but otherwise you risk making all that artist's mistakes into your own bad habits. ^_~

Before trying to define a style for yourself, try to see if it'll come naturally as you learn. If not, it's still worth a shot as there's a lot you'd be better off getting a hang of first -- anatomy, color/values, shading, flow, perspective, etc.

As for heads... maybe someone else can help more. There's definitely some tricks, mainly involving 'seeing in 3D', so to speak, but I havn't figure many of them out for anything other than avians. ^^;

Thanks for the tips! *high paws*