I'm going to have to agree with what has been said with poses and instructions.
I will say this, and I know I'm a new guy here so I do apologies if this may cause any problems, which I hope it doesn't..
I'm not sure how many portraits you've taken in the past, so I will go by what I see in this thread. (edit* just noticed it was your first photoshoot)
Here's the thing, I think you have a great potential to be outstanding at portraits and photoshoots. The scene was a great choice (beach). I think with a little bit of practice, you will be able to achieve brilliant portraits. These were just fine; though, I agree with the comments on instructions. I think you should try to become comfortable at giving directions for poses. The photographer should always be confident and comfortable at giving poses to his or her model. Otherwise, it could turn out a mess.
Seeing how this was your first photoshoot, I do think you did great. Some shots were a little... "odd" per-say. Not that they were bad, but they could've been modified as far as positioning and composition. For example, image #2, it's not a bad shot, but the model can't be seen that well. Her facial expression and emotion can't be seen.
Good place to take the shot, but the pose is a little off... It almost seems like she closed her eyes before the shot was taken. I think a closer shot of her face looking at the camera would have been great. Especially black and white with the beach and water in the background. For many cases, you want to express the subjects emotional feel, so it's good to have he or she looking and posing in a way that attracts the eyes deep into the photograph.
But we photographers all have our own opinions on what is nice and what could use a little work.
I think you should definitely continue your portrait work, as I think you will be outstanding with more practice and comfort.
In my opinion, one of the greatest forms of learning is to imitate other portraits you see that you like. Search for portraits around forums, and photography sites until you find photos you like. Look at the photo, and remember the pose. Use that pose in the future, and then modify it a bit. Background, arm placement. It all just takes practice.
I hope I could help, and I hope I didn't sound rude and/or insensitive in any of my sentences.
Wish you the best,