I've received plenty of writing advice from friends, colleagues, and the omni-present tide of people on twitter who want me to buy their books. Some of it's valuable, some of it's junk, and most of it is terribly cliche. Seriously, 90% of writing advice is some variation of "write every day" or "show, don't tell." While it's probably great to write everyday, let's admit that's not likely to happen when you have a baby, a job, or anything else in your life that doesn't necessarily follow your ideal schedule (mad pet vampire hamster?).
So other than "write often, and don't give up even you can't write everyday," the best advice I've received is to read your writing out loud while you're editing, and find a good critique partner or writing group. I had a great advantage when I first started writing--I taught eighth grade. In fact, I started by writing a series of reader's theater plays for my students to read aloud in class. That meant two things: 1. My writing was regularly read out loud, and 2. I had an audience of brutally honest teenagers to tell me what they thought about it. This inspired, or rather terrified, me into improving my craft.
It's amazing how much you learn by reading your work out loud as well--awkward sentences or blah dialogue becomes far more obvious. If you're writing for a particular audience, say young adult or middle grade, then it's especially helpful to have someone of that age group read your work. It's fine for young people to stumble over words every now and then, but if they have to struggle too hard with your material, or seem confused, then you might want to look at ways to clarify/simplify your writing. Plus, you'll know immediately if they think your story is boring or stupid.
I know it hurts sometimes to hear criticism. I'm pretty sensitive myself. But I'd rather hear the truth from a critique partner or writing group than an angry anonymous reviewer on Goodreads.