My advice to you, in terms of fiction at least:
Just sit down and write. Know and expect that at least the first million words of what you do write will not be publishable. Get your style down straight through practice,
then look for advice elsewhere. Accept critique and expect it to sting. Don't argue with people's critique of your work - there is no such thing as reader error.
In the meantime, the single best resource for writing in general is William Strunk's
Elements of Style.
Good luck.
By the way, kthdsn - just hit the Submit button and don't worry about it. If people think your work isn't worth reading, they just won't read it - big deal. It's not as if you've lost anything by pressing Submit over not pressing it.