definitely do it on a nice day, with warm sun and clear blue skies. i go to U of M and i have the Nichols Arboretum across the street; amazing!
Nichols Arboretum - Wikipedia, the free encyclopedia
easily one of the best places to go. so i 2nd the recommendation with nature. its just nice being outdoors, no confined spaces, beautiful plants/flowers to get lost in, and i love seeing people holding hands and walking around.
if its you're first trip, i recommend doing it with a bud so you can both ground yourself incase you lose grip on reality.
edit: just thought of this one. bring a note pad and pen. i usually have some great realizations that i love to write down.
an ipod and camera could be fun too...
personally, i hate going back to my apartment while still tripping. its easily to go from having an amazing time to having a bad trip, and then feeling trapped. when you're outside and you dont like something, you can just walk away and immediately feel better.
one last thing, i also dislike interacting with friends who are not "with" tripping, and i'd rather them not know i'm tripping and any possible judgement from them. its lots more fun to just hang with random people you meet or friends who you know are cool with tripping on shrooms. personally, i turn my cell phone off and leave it at home. i figure any sort of calls can wait a few hours, which reduces any sort of risk of having a phone call influence you when you are in a different state of mind which may cause a bad trip.
... just some of my personal preferences for tripping...