You don't really "trip" or "hallucinate" on DXM... it really just makes your body feel different, and change touch sensations and the like. It's fun to do occasionally.

As for where you can get it, I know that you can extract pure DXM powder from the cough syrup, but I'm not exactly sure about the process or anything. Search on the boards for DXM, I'm sure you'll find more information than you'd ever need about DXM.

Also, Erowid.org has a great bit of information on DXM, naturally..

Good luck!