The best way to tell for sure is to search the car for the build sheet or send 35 bucks to Pontiac Historical Services for a copy of the build sheet. There are ways to develop a strong opinion whether it's an SE or Clone, but without the buildsheet nowadays it's getting impossible to be sure you have a genuine article.
Look for all the gold accents. Dash Bezel, headlight grilles, steering wheel spokes, right wheels for a SE of that year, etc. If your seeing stuff like that and can't find the build sheet it would be worth the 35 bucks to know for sure. Post some pics... I'm sure there are folks here that could give you a better idea of it's SE status and value.