um
wow.
dont do that much your first time. its awesome, but its a whole new experience different than anything ive ever done.

AND MAKE DAMN SURE that DXM HBR, USP is the ONLY active ingredient. dont get time release shit. try around 300-400mg your first time. (1 4oz bottle of robitussin) and you will be good.

if you search for "first dxm trip" or something like that in the forums.. there are countless people sharing their stories of it. read about it first

http://www.dextroverse.org/whatis.html
http://www.third-plateau.org/faq/dxm_faq.shtml

read both of those if you've never done it.