Alrighty, some of the older hands around here will know me as the Automotive and Landscape junky, Well I got asked to do some human portraiture and it was my first full portrait session with 2 sisters sitting in. I'll say it now: I was shaking in my shoes! There are others but I think these are pretty much the better ones of the crop. C&C accepted.
I think they are fine for your first attempt, I would try next time to crop a little better like the shot sitting on the wall and also sitiing on the stairs. My oppinion and only my oppinion the background was a little distracting.
They look pretty good, well done. Some of them look a little bright...her face in the last one, for example. Also, I think they would benefit from some fill light. In most of them...it seems that both their eyes are too dark. Some catch lights in the eyes would also help.
Nice job! In #'s 1 and 3, a slight rotation would help slim some. Shooting people square to the camera can emphasize their width. Most people don't appreciate that, LOL!! Self included.
#3 is my favorite of this set. I agree with all the advice given about fill light and background choice, too. Portraits is a big change from cars, I bet you'll have fun!