My suggestion; Robitussin Cough Gels or Rite-Aid/generic brand Tussin Cough Syrup[hell, if it all taste like crap, why pay more?]. 800-1200mgs for a full blown trip, but only about 500 if you're not familiar with tripping or just don't wanna puke all night. Like quite a few people have said before me, please avoid Coricidin, and make sure that whatever you choose contains ONLY dextromethorphan hydrobromide[there are several different derivatives but I don't know the details].
Which reminds me, does anyone know any stats on that Delsym stuff? I think it contains dextromethorphan polistirex, but wasn't willing to be a lab rat on this one.
Also, I've found that syrup only nauseates me *slightly* more than gel caps, but the only way around it for me is to smoke some weed at the same time. A friend of mine use to like to drink liquor with it, increase the drunkish effects, but I dunno how he stomached it. And I'm a smoker, which I've come to find out that not only does nicotine make you pretty damn sick while on it[that much I figured out on my own] but it also blocks the receptors in your brain that are effected by DXM[that my dumb ass had to look up].
Finally, I've read that grapefruit juice[and some others, forget which] contain chemicals that will INCREASE the visuals of the trip[dunno why, but I have had some success with it]. P.S., as always: Know your mind, know your body, and know you drug[and have a blast!].