Listen to published authors when they have something to tell you, because they know what they're talking about. They can provide you with valuable information. Don't scoff, even if something they say sounds weird; there's a reason they're saying it. Example: An author I met at the conference last year told me I should make the effort to attend a romance conference (I don't remember which one). She writes urban fantasy. I scoffed. Why? Because I don't read romance and I certainly don't intend to write romance. She pointed out that there are often elements of romance in all different kinds of books. Guess what? She was right. I wasn't far enough in my novel yet to truly get it. I had no idea how hard writing the relationship portions was going to be. Now I know, and I kept wishing I knew something about it, because I felt a tad uncomfortable writing anything that was in any way romantic or having to do with interpersonal relationships between male and female. More accurately, I felt squicky about it. Given, I am not in a position to be running around to a bunch of conferences--it took quite a few hours on ChaCha to make the money to go to the Pikes Peak Writer's Conference this year--but it was still very valid advice, and if I have the opportunity at this conference or another gathering to learn about writing romance/interpersonal relationships, I'm there. I won't scoff again.
Listen to unpublished authors when they're speaking from experience. They're learning, just like you and me, and we learn from getting out there, making mistakes, having experiences. Share those experiences and build on them.
Listen to agents when they talk. Don't get offended when they criticize. Take in the information and use it to make your work better. If you get a response to your query with feedback, that is a positive step (unless said feedback is something like, "Please do us all a favor and never write another word," in which case that could be a problem). There are good rejections and bad rejections (or so I've been told), and good rejections hopefully come with feedback and/or after having been asked to submit more of your novel. I'm not saying to not fight for your novel; I'm just saying to take in constructive criticism from those in the know and mull it over a bit.
Listen to yourself. When you have ideas, when you want to write or when you need a break. If something doesn't feel right in what you're writing/reading, chances are you need to change something. If you've read your own novel 20,000 times and can't bring yourself to care, listen and take a break. Give it a week or so and come back to it.
Listen to the voices in your head (unless they're telling you to do naughty things, in which case you should probably ignore them). Those voices are your muse.
Listen to those who critique your work for you. This does not mean you have to make every single change they suggest, but it does mean giving their words a fair shake and a neutral ear, as hard as it may be to have your baby criticized. It's especially important to listen when several different readers have the same feedback. Chances are, those who purchase your book later will see the same problems.
Of course, listening is easy. Accepting it is a whole new animal, and one I'll be working on right along with everyone else.
Did I miss anything? Who else should we be learning from? How are you at listening?