I think you did a real fine job! Especially for a first effort! Mind some constructive criticism?
#1: Real nice! I'm usually not a fan of the horizon running downhill, but somehow it works for this pic. You have placed their hands very well; human hands are generally ugly. Nice little sparkle to the eyes, did you use fill flash or a reflector? As the photographer, you're in charge of appearance; have the young man tuck in his shirt (back). Have the young lady run a brush through her hair just before the shot to blend/smooth it. You blurred the background quite nicely and it really makes the couple stand out! I'll bet you were very pleased with this one!
#2: Cute! Love how she kicked up her foot! Try not to photograph the back of a ladies hand; have her rotate it slightly so it presents the edge. He looks stiff; as if he's trying to pull away from her. Have him cock his head slightly toward her. His hand looks awkward; it should be somewhere or doing something. Have him drop it in his trouser pocket, rest it on her hip, grab her sash, just something... Try not to cut part of the body if you don't have to; his left shoe... Nice job on the background and making the couple stand out from it!
#3: Yes, they are too cool for words! The guy on the left is a little too edged; you miss out on his vest and his tie. The guy on the right has a perfect angle for a gentleman. You have the two classic "guy" hands-in-pockets versions; thumbs in and thumbs out. When you pose a gentleman in a suit/tux, pull the sleeve of his dress shirt out past the cuff of the jacket. Then have him put his hand in his pocket. You should see a sliver of shirt cuff and a sliver of skin... If they're friends, try to close that gap between them somewhat. Distance between subjects in a portrait strike the eye as emotional separation/aloofness... Again, great job on background selection and selective focus!
I don't know where you shot these, but that location would definitely go into my book as a great portrait spot. Start developing a personal location guide; note location, time of day, weather, and the size of group a location will support (single, couple, or a family of 10...) Hope this was helpful!