Re: ...what to eat and where to start???
That's a little hard to advise since you have very little control over your meals. Since you only need to lose a little, and from the sound of you, it sounds like your young, a little bit of mindful choices in what to eat would be good. There's a user here by the name of momonline that advocates a diet by Dr. Shapiro... that may be a good start for you. Hopefully she'll read this and advise you. But to start, cut back any sugar you can... that includes junk food and sodas... and if you can, cut back on starchy foods such as pasta, bread, potatos, etc... they're empty calories that just get turn to sugar, and thus fat, in your body.
Also, are you active? If not, a little more activity may help.. jogging, sports, cardio machines, maybe some light weights. 29 lbs over the summer is definitely possible, though it will take some work... it might be a little harder for you since you have less control over what you can eat.