As for critiquing:
On the first one I would say get more of their faces.. and more light. The little bit you can see is very dark. The camera angle kinda throws me off too.
Second: Lighting is nice, but your subjects are in the bottom at least half, if not third of the photo. Get more of them in it; at least have the woman's boots in the photo. Her tilted head looks a bit.. painful too I would say. Have it be more "natural" or "comfortable."
Third: I like it, but seems dark at the bottom and really light at the top. Some work with the levels could help that one.
Forth: I really like this one. This is the one that caught my eye.. but I would like to see more of the guy's face. That is all I really have for that one.
Fifth: Get at least the bottom of their feet. This is a common tendency.. I used to do this a lot too until I was scolded a bit for doing it. But make sure you at least get your subject's feet in photos like this. Either that or get closer and have them be the frame for the photo (meaning you could crop this so there isn't so much space above their heads and it would look great.)