Need help on my TSA flight endurance glider?

Im heading to the tsa competition in a couple of weeks and signed up for "flight endurance", a competition where participators make a glider that's supposed to launch using a rubber with a propeller and stay up in the air the longest. I just finished my drawing of my glider and i was pretty happy about it, until i ACTUALLY looked up the laws flight and how flight actually work (i mainly look up lift, but not alot, so im clueless) my glider dwindles in efficiency when compared to a href="http://www.freedomflightmodels.com/images/catalog/Fun%20Science%202010.jpg" rel="nofollow"http://www.freedomflightmodels.com/image…/a . what i need to know is; how do i make a good glider?