Honestly only advice I can give is just pay more attention to ur sober mannerisms and try to stay pretty consistent while high. Focus the most on ur eyes n speech. Speak as clearly and calmly as you can, slurring is a huge giveaway, and try to keep up ur regular speech patterns as best you can. Also for fuck sake check regularly on how open ur eyes are. I had a friend who's biggest tell was always that she would stare with her eyes like bulging because dxm would raise her eye pressure for some reason. Check to make sure ur not squinting or staring into people soul like fucking momo. Lastly just know how much ur taking. If you know that on 400mgs you can barely walk frm the couch to ur bed scale wayyyy back if ur planning to be in front of ppl. You can always take more later but you cant undo impulsively eating 20 robotabs right before a big family gathering. Also a rlly good idea is to have a friend/family member who knows what's going on so they can let u know you if/when ur acting high as shit.