All I can say is to do the best you can do! Pick or create a pattern that really excites you, choose the fabrics that YOU like, not what others may think...this because you won't be happy throughout the making of the quilt if you continue to look at that one fabric that someone else chose over your choice wishing you had picked the other. A little thing like that can show in your work. I always shop for fabrics by myself when it is a major project that I want "just so." Most of the time my choices are questioned by friends until they see it all put together.
Once you have the fabrics and the pattern just give it your best shot. I couldn't believe my first win...actually a friend and my DH entered it for me because I thought it was a really stupid idea to put it in a show.