Originally Posted by Freebase Dali

If you're getting dried shrooms (assuming you're getting a P.Cubensis strain, which is the most common), you'll probably want to weigh out no more than 2 grams for your first time. There's a lot of factors that go into it, but you'll get off for sure on 2 grams. There's no reason to half ass it.
If quantity is low between all the participants, I wouldn't go below 1 gram for each of you. 1.5 would be the nice comfy middle ground... but if you have enough for 2 grams each, I'd go that route because you're not going to get much off a half a gram each if you save some, especially while your tolerance is still high from the first round.

If you're getting fresh mushies, that's where things get a little iffy because the gram amount is going to be a lot higher. For fresh I'd go about 18-20 or so grams each. It's a lot more variable than dried. You should shoot for dried because you'll get more consistent dosing.

I'll write more later, as I have a date with crawfish.