First, good for you for wanting to start one at your high school– one wasn't started at my rather conservative old high school until after I had graduated. The GSA has certainly made more people feel more comfortable about being out (versus the just two really open people at a school of 2,500 when I was there!)
Second, my college's GSA is called the LGBTSU (Lesbian-Gay-Bisexual-Transgendered-Straight-Union, although I'm sure you could figure that out on your own just fine!), actually Kaleidscope LGBSTU, to be more inclusive, although the name's still not totally inclusive.
Third, this may have already been covered, but getting support from teachers. While my college's student body and administration is conservative, the professors are very liberal and supportive of such organizations. They'll wear ribbons on pride days and show up to events. We also have a list of faculty and staff (as well as fellow students) who are queer or GLBT-friendly for students to visit or call for support in an emergency or just to chat.
I know there is not as much freedom in high schools (well, at mine at least) but I'm sure there are a bunch of teachers who would be willing to, for example, post a sign on their door that designates the room as a safe space.
Getting teachers involved is great for both publicity and support– concerned students can feel safer there and homophobic students know their ignorance and harassment won't be tolerated, at least under the watch of that particular teacher.
"Tear up the cloak of indifference that you have wrapped around your hearts! Make up your minds before it is too late!" ~Sophie Scholl
(Edited because I apparently couldn't spell the acronym of an organization I was an officer in so should know better!)
[This message has been edited by Ecofem (edited 07-28-2003).]