Last time i got someone high was a nightmare, she pissed me off so much. I was at a party smoking a spliff with some mates and a girl (a year younger than me, 15) asked if she could smoke some, so she took a drag, and went crazy, she was laughing, then stopping and looking serious then laughing again, then she lay down and screamed and cried for 2 hours (2 FUCKIN' HOURS!!) and wouldn't shut up.
The whole time i was telling her it's just the weed and that nothing bad's going to happen, but she really believed she was going to die so i had a go at her and told her to stop being stupid (she only held the smoke in her mouth, from one drag) and she sort of calmed down. I walked off, and when i got back supposedly she had settled down and buggered off home.
So as for getting people high for the first time, make sure they can handle it and aren't complete idiots about it lol.

Ps, also she had pissed me off a while back and shit so that's why i had a go at her and didn't have patience for her messing the party about