(1) Invest in a milligram scale (.001). They cost the same (roughly) as the .1 and .01 scales. You can get one on amazon or ebay for like $25, on amazon you can have it in 2 days (if you have prime anyway). Absolutely no excuse to not get one, your scale is not going to cut it if you're dealing with research chemicals.
If you had a phenethylamine (like 2C-B or something) you would be able to dissolve the whole amount in some vodka or similar alcohol, say 250mg in 250mL of liquid, and then you could use an oral syringe (you can get them for free or buy slightly nicer ones at a pharmacy, they're just used to measure liquid medicines) to accurately dose yourself without a scale... you would know that each mL of liquid contained 1mg of the chemical. Of course, you have to weigh the total amount first to make sure they sent you the right amount, you can't assume they did (I've had places send me twice as much as I paid for before). Your scale would probably work fine for that, because if it was off by 10mg, that error would be divided across all the doses so you'd still be pretty accurate with liquid measurement. HOWEVER, with tryptamines (like 4-AcO-MiPT), you shouldn't store them in liquid because they break down rapidly (unlike phenethylamines which will last a long time in stored in a cold environment in liquid). So this method won't work in your case (but it's good to know about if you end up getting some other thing, especially very potent things where even a milligram scale can be too inaccurate).
Do NOT eyeball it/try to divide it into lines, 2 piles of powder that weigh the same can look quite different especially if the powder is fluffy. There's no good way to do this, especially if you're new to this sort of thing (but really, no one should ever eyeball, it's irresponsible).
I wanted to give you some general information since it's important to learn, but what you need to do is order a .001 scale, that way you'll be safe.
(2) Don't snort it, I mean you can, but the effects are better orally. I just put the powder in my mouth and swallow but some people can't bear the taste, so yeah, you can mix it in liquid and chug it down (it won't break down that quickly, it breaks down over the course of days/weeks/months), or put it in a gel cap, or parachute it. However you feel is best to get it down.
Enjoy! 4-AcO-MiPT is a great substance, one of my faves. Please come back with any other questions you have.