Recently, I've had a few close friends ask for my advice in getting their books published. While I don't yet have an agent or a publishing contract myself (I'm still in the beginning stages of the process - finding the nerve to send out queries to literary agents), I'm happy to share the things I've learned.
The best advice I can give aspiring authors (like myself!) is to get to know other writers. I've learned so much from my associations in the SCBWI (Society for Children's Book Writers and Illustrators) and the MWA (Maryland Writers' Association)! Get involved in a good critique group, with other serious writers who will have the courage to tell you when your beloved manuscript just isn't very good yet, and who will have the skills to tell you what you can do to improve it. Good critiques, while not always pleasant, are absolutely essential to a serious writer!
I've also advised friends to utilize the immense amount of information available on the Internet for writers. A quick google search will give you pages upon pages of blogs and websites full of tips, tricks and techniques. You can take online writing courses (some are free, some require a small fee), enter writing contests, read interviews, the list goes on and on!
One of my favorite writing resources is the blog Literary Rambles. The interviews with literary agents on this blog have been ever so helpful in my quest to find an agent of my own. Almost every agent I've considered querying has done an interview here, and while it's always a good idea to verify any information from an interview with the submission policies on the agent's official website, Literary Rambles is a great jumping-off point in the research process. In addition, they've posted some great interviews with authors, book reviews, even Q&A sessions with middle grade readers! They've just hit the 2,000-follower milestone, and they're running a great giveaway contest (through the 28th)! Head on over, check out the site, and enter the contest while you're there :)
Other websites/blogs I've found helpful: (This is by no means a full list, just a sampling of what I've discovered in my searches.)
8 Fiddly Things You Can Do to Your Manuscript to Make Your Editor's Day
Verla Kay's message board for Children's Writers and Illustrators
Katie Davis: Author/Illustrator - Webinars
Seven Ways to Turn Writer's Envy into Inspiration
Authors Make Their Own Success
Good luck & Happy Writing to you all!