The bending of the wrist is a beginners problem which will go away with training and with the right instructor. There are many ways to punch and get power in your punch. I prefer the two knuckle punch as it is less likely to break the article below is from Master's Magazine originally:

http://alljapankarate.com/index2.php?opt...

To correct the writst and two knuckle punch this get a pencil and put it between your pointer and middle finger then start to punch slowly making sure that the pencil goes straight. good luck

Find a teacher before you hurt yourself trying to figure out how to punch. Wrist injuries are no fun and breaking your wrist is even less fun. Enough injuries will leave your wrist permanently weak. So be smart and sign up for classes.

The real question is, why are you not asking an instructor what you are doing wrong? Without seeing your punches I can't explain, though my guess is that you probably don't have a straight wrist.

Put fist near hips, punch foward and rotate your hands. Basic Karate stuff.

get a punching bad and start whaling on it, youl figure it out

I am clueless with punching I know to use first two knuckles but how do I throw it? How do I know if my fist is in it's proper position? When I hit sometimes my wrist bends due to incorrect hitting I don't know what I do wrong where do I punch from I don't get it. Please help step by step:(