I wouldn't do them outside/in public your first time unless you are a ways away from people. Seeing people you don't know while tripping is an easy way to get paranoid and anxious.

If you do them alone, just make sure you have somebody with you in the house or at least on standby to help you out if you need it. Sometimes you can get stuck in thought loops and need someone to talk to before you start feeling better. Like /u/Grampley11 was saying though, shrooms are a very personal experience. I've only tripped with other people, and I can attest that it is hard to get introspective when people interrupt you, no matter how good their intentions are lol.

3g seems to be the amount most people I know take. It'll get pretty trippy, but not too bad.

Don't let me scare you though! Shrooms are amazing, some of the best experiences I've ever had in my life. Definitely find some soothing music you like, maybe put on some planet earth in the background and you'll have a blast. It's just important to prepare everything ahead of time, because once you're gone you won't be able to do much of anything lol.