Wow.. not being able to comment on the photographer is.. hard.
Given that he's the one taking the photo, choosing the angle, choosing the lighting. What you need to improve on:
#1 - no fun factor. You don't look like having fun, despite your big smile. Body posture's somewhat stiff/strange. You'll do well to tell the photographer not to focus on the background but you. If you're sticking out your hand to look like you're holding something, make sure the photographer gets it. If you want to look like you're interacting with the environment, make sure you are.
#2 - People never look good when they have 4 black dots on their faces. 2 eye balls and 2 nostrils. Tilt your head slightly so it won't be so obvious. Also, you'll do better if you tell the relatively inexperienced photographers not to take that angle. If you're trying to "interact" with the environment again, and it's a relatively dark place, next time don't bother. If you're looking at your nails, I'm sure you can choose a better location. You'll also improve if you tell the photograher in this case to include your body. 1 floating hand is disturbing
#3 - You should know when you normally smile, more of your upper gum will. Not that it's something to nitpick on, but this is close one of your nice angles, but you MAY want to consider not doing so many shots from below. If taken from a slightly higher angle, I think it'll be good I'm not sure what lense the photographer used, but it should be a wideangle and he should be standing close to capture this head shot. Since your hands aren't an issue, next time lift up your arm so that it won't be squashed against your body. It's a quick fix in photoshop, but not everyone will bother.
#4 - Perhaps next time lose the beads. Doesn't mean don't take any, but i think perhaps avoid full frontal. #3 makes your face nicely angular and 3d. This one will usually make your face look flat. It doesn't mean you CANNOT take full frontal, but thel lighting conditions should be suitable.
It'll do you good to request the photographer to take a bit more of the background (to avoid cropping off the hand etc), not to focus on your breast (causing your face to go oof).
#5 - What's there to say? A classic example of everything bad. Tree growing out of the head, lines poking into the head, under exposed face, distraction more prominent than subject (the rhs thing), un-natural body posture...
Oh right, to improve, for you... make your body posture more natural. No normal human will normally have their heads 90 degrees. Perhaps take note on it? Er.. avoid frontal? Er, get the photographer to focus on you instead of the background?
#6 - Floating Fist! Nevermind that I can't get a sense of distance from the fist to the body..
You look too posey, too fake. Nobody punches like that with the shoulders drawn up to their cheek. 1 hand is not better than 2. Try to make sure both hands are somewhat seen.
#7 - your brother's photo.. Easily one of the better photos of the bunch. Now if only the focus was correct.. Personally I think lose the hat next time, lose the beads too.