It's hard to measure dose too, you never know how potent your mushrooms are, so you have to expect a mindfuck, it's what they're for. They're the most intense drug I've ever had, that's why I'd recommend them as a first time psychedelic, because I'm sick like that, but please make sure you're with good friends, at least one who is more experienced with mushrooms & you don't need to see anybody who isn't tripping with you for the next 8-12 hours.
As long as you get the right mushrooms then the only dangers are having the most intense experience of your life & doing something stupid under the influence, or getting caught by somebody you don't want to see you tripping, because it'll be really obvious you are.
You can make decisions on mushrooms, but they're often not the greatest ones, you'll be in a weird state of mind & extra suggestible. Don't drive, go to work/school or operate heavy machinery. Best to have an empty house with a few friends, or go outside & find a quiet place where you & your friends wont be disturbed for 8+ hours. So, avoid having to make any decisions, or see anybody that wont want to see you tripping, if you can't do that, wait for a better time.