You don't say at what level you are at present -an absolute beginner; or you take snapshots occasionally; or you are a keen amateur or what? Take a look at the website I have linked below.  Betterphoto has hundreds of members of all skill levels and hold competitions each month. The link tells what the judges are looking for in the members' submissions to the competitions and is a good place to start. While you are there take a look at the members galleries too; there are thousands of images and can give you some idea of what's out there and which ones the editors/judges set aside as their "first picks", and then their "finalists" and then the "winners" in each catagory.  Good luck,  Pete     

http://www.betterphoto.com/contest/guidelines.asp