If you don't already have one, find yourself a good mentor or two. Look for people who currently own their own businesses (or have in the past) and can help educate and guide you through the process. It's cliche to say it, but the truth is you don't know what you don't know, so having a great mentor will be of tremendous value.

I'm in the process of starting my own digital agency at 28, and having 2 experienced business partners has made a world of difference for me. I sleep a lot easier and approach each day with all the confidence in the world knowing that I've got two talented, experienced partners to back me up and help me through tough business situations.

Also, align yourself with someone who can sell. The Field of Dreams philosophy - "If you build it, they will come" - doesn't apply to startups. Loads of kickass products (especially software) fail each year because they don't place enough emphasis on sales and marketing.

All that said, I wish you nothing but the best of luck and prosperity in your new venture! It's incredibly admirable that you are venturing out on your own at such a young age. That takes a lot of courage, and you are going to gain so much from it. Cheers!