Its not open to the general public. With that being said, there are ways for one to attend. Back in 96, a friend and I had a local gunshop order two badges for the owner and one employee. We paid him $50 for the badges and we went to SHOT. In 1996 it was in Dallas, so the trip was and easy one. Myself wearing the owners badge, a lot of folks were trying to sell me stuff, which of course I could not buy. I did come home with a bunch of free stuff tho. If one gets the chance, go!
It's cheaper to join NSSF than become a dealer. NSSF members can attend. It's $100 for the 4 day pass but at least you can attend. LEO/Military can attend also.