The way it most often works in my experience is that whatever sign you are in the zodiac, and what that sign corresponds with, is your element. I am a Gemini, so I am an air. Though there are also other methods to help with finding it out. For example, there is the LaVeyan synthesizer clock, which can help if you have no clue (http://api.ning.com/files/veSS*NnFynT1FjlYyv0K5JX0iRGZxlknD0iUug1vxvvrorqpm4l0M3jONFpvQdvtHcQhhPJ8F4J-zOZ*MKArwT2PDNaHYQb0/TSWclock.jpg)h
Also, you can try meditating if this works not. Another possibility is that you are a cusp, which is when one is more than one element, this is generally uncommon though possible. Good luck!