dxm is an incredible drug, but mind you i don't really do drugs like i used to, so i haven't done it for a while.
i started using dxm taking doses as small as like 400mg-500mg. then increased to like 1000mg. my largest dose ever was 3.2grams, which was freaking incredible. the problem is that when you take large doses, you'll black out. so you need to continue taking large doses every day for like a week, and then the time when you black out, you won't black out anymore, and it's freaking incredible. most incredible trip ever. better than acid, shrooms, whatever. dxm is the way. but don't go and take 3.2g off the bat just coz i said i survived it. i felt like i was going to die the whole time and it ruled, but that's just me. start small and build up over the course of a couple of weeks if you want to get to that point. just like with any drug, don't be completely retarded. your body/mind is a door to the kingdom and if you keep slamming a misshaped key into it you'll fuck up the lock.
just be careful. dxm is easy to get addicted to. i found myself capping and stashing and popping 300mg caps throughout the day everyday. i would get something akin to heroin withdraw when i didn't have it, but more physical, less mental when withdrawing from dxm. really sucks, so watch yourself with that stuff. what sucks even more is when you run out of the powder you ordered from research companies back in 2002 and find yourself stealing coricidin or dexalone from your local grocery store daily to feed the addiction.
when i was using dxm all day every day for an extended period (2-3 months), the world seems very glassy and distance. i felt safe and secure, like i was separated from everything. (yes, yes, y'all, it's a dissociative). helped with my anxiety and depression, but of course withdraw produced extensive anxiety.
dxm is more for learning about yourself and your life and where you need to be. kind of like how some people like to shroom occasionally to sort their shit out. other types of people dex every once in a while to sort their shit out. i think it has a lot to do with personality and placement.
i can't use shrooms or acid anymore really. i just feel like i've learned everything i needed to learn from them and as soon as i start tripping i feel like i'm wasting my time. i still OCCASIONALLY like to dex. i think last time i took 1.5g, maybe like 9 months ago. if you feel like u need to examine yourself and your life from a distance, take 900mg and chill with some chill tunes in the dark.

doctor's orders, g.
one other thing. opiates + dxm = not a great idea, HOWEVER, dxm is a morphine analogue and small doses (i'm talking 30-50mg) daily will keep your opiate tolerance down, but don't expect it to keep you well if you're w/ding from opiates.
cheers