DXM is found in over the counter cough medicines such as Robitussin extra strength and Vicks 44, as well as in lozenge form and (pure) powder. Basically it tastes absolutely horrificly vile, and I suggest reading up on some techniques on the websites at the bottom of this post as to how to take it without chucking, as chugging 2 or 3 bottles of cough syrup is unpleasant. For your first trip you should only ever take 100mg as a precautionary thing, as some people have enzyme defincies which mean they cant oxidise the drug (or some such).
DXM works on several plateaus namely up to 4 - though there has been reports of a fifth plateau that usually involves puking, the diarrhea, etc as well as a few reports of NDEs.
As an overview, first plateau is more like a party drug and usually involves taking 1.5-2.5mg/kg of your body. For many the most exciting part of first plateau is music; and I assure you that you will never experience music quite like it without dex
Second plateau is roughly the same but I dont reccomend it as a party drug - you will most likely have trouble walking/talking etc. You can have mild hallucinations on second plateau. Third plateau is the highest I have gone and involves deep hallucinations, OBEs (though much different to what I have heard "natural" OBEs involve.. I have yet to have a natural OBE so cannot make the comparison), the trippy mind exploration stuff . I have never been to fourth plateau but hear it is similair to third except much more profound and often involves meeting of entities/angels/"the DXM god" (no, seriously.. hehe), and removes you from the real world to the point of being paralysed, incoherent and to any person not on drugs absolutely totally whacked out 
I reccomend doing some reading before taking some DXM as their are some important precautions and such that you must follow... namely I never buy cough syrups with anything but dextromethmorphan in it, as any other drug mixed in can either be harmless or kill you and it takes much experience and knowledge to know what not to mix with dex. On that point, never ever take Coricidin. I think it has castor oil or some other ingredient not listed in the ingredients and has been known to have killed 6 people and in some cases make users bleed from their eyeballs, anus, ears, etc. Just do not use Coricidin
One more thing - after you take your first hit drink some OJ... the dex is mildly acidic and OJ is an alkaline which should help to settle your stomach and reduce the sickening feeling.
http://www.third-plateau.org/
and more specifically the famous DXM FAQ - brilliant.
http://www.third-plateau.org/faq/dxm_faq.shtml
- Ashfo
DXM works on several plateaus namely up to 4 - though there has been reports of a fifth plateau that usually involves puking, the diarrhea, etc as well as a few reports of NDEs.
As an overview, first plateau is more like a party drug and usually involves taking 1.5-2.5mg/kg of your body. For many the most exciting part of first plateau is music; and I assure you that you will never experience music quite like it without dex
Second plateau is roughly the same but I dont reccomend it as a party drug - you will most likely have trouble walking/talking etc. You can have mild hallucinations on second plateau. Third plateau is the highest I have gone and involves deep hallucinations, OBEs (though much different to what I have heard "natural" OBEs involve.. I have yet to have a natural OBE so cannot make the comparison), the trippy mind exploration stuff . I have never been to fourth plateau but hear it is similair to third except much more profound and often involves meeting of entities/angels/"the DXM god" (no, seriously.. hehe), and removes you from the real world to the point of being paralysed, incoherent and to any person not on drugs absolutely totally whacked out I reccomend doing some reading before taking some DXM as their are some important precautions and such that you must follow... namely I never buy cough syrups with anything but dextromethmorphan in it, as any other drug mixed in can either be harmless or kill you and it takes much experience and knowledge to know what not to mix with dex. On that point, never ever take Coricidin. I think it has castor oil or some other ingredient not listed in the ingredients and has been known to have killed 6 people and in some cases make users bleed from their eyeballs, anus, ears, etc. Just do not use Coricidin
One more thing - after you take your first hit drink some OJ... the dex is mildly acidic and OJ is an alkaline which should help to settle your stomach and reduce the sickening feeling.
http://www.third-plateau.org/
and more specifically the famous DXM FAQ - brilliant.
http://www.third-plateau.org/faq/dxm_faq.shtml
- Ashfo