This should definitely help bring on your skills Hali and its a creative way of doing it too!

To give you a brief feed back on each one:
A. Its a bit generic. There's noting interesting going on in the picture especially with the composition. I would personally move the can further right but keep the DOF. However to add some interest, why dont you set up the shoot in some grass outside?

B. #s 2 and 3 are IMHO shot at the wrong angle. You should be at the front left/right to capture more emotion, feeling and movement in the image.

C. Nicely done

D. Underexposed - but the composition is nice. Try exposing for midtones and use your flash to fill in the shadows.

E.. Im not keen on this one. The crop and angle dont sit right and the eye is to narrow. Rather than take the image head on, go from a slightly higher angle to open the eyes more and get some great catch lights.

F. I really like the composition and idea of these, but i think your exposures off and Im not a fan of the orange white balance. It may be a personal thing, but this is what I would have preferred ..
http://ladyfi.wordpress.com/2009/01/09/fire-and-ice/

G.#1 is underexposed=and the WB is off (blue) but otherwise nicely done.

#2. Cant fault it. Best so far.
#3. Beautiful but watch your not underexposing

Ill come back and look at the rest later... Good Start though! x

Thank you so much for the time you've taken to comment, I've found your comments really helpful (and gentle) Getting the exposure right is defiitely something I'm struggling with, though hopefully this will improve in time.

Perhaps for the 2nd half of the year I'll go back and shoot the same subjects (where possible) and see how I can improve.

I can see that your are struggling with exposure. Are you metering the scene at all? And what setting is your camera metering on?

Sorry, if i seem a bit "to the point" im not very well today x

No that's fine (hope your not too poorly and will soon be feeling better).

I hadn't been. I tended to leave it on evaluate. Until recently I didn't even have a clue what the histogram showed (and still need to understand a lot more).

I did try setting the exposure by metering on a specific point, but didn't really know what I was doing.

So all in all, I've got a lot more reading/understanding to do!