I want to loose 40 pounds over the summer?

ok so im 14 and i weigh about 160 and im 5'4''....i think thats how much i wiegh on a normal scale it says i wiegh about 154 sooo lol i dont wanna b that fat well any ways i carry my weight pretty well but i reeaaallllyyy want to loose weight im about to start high school and i really want have the best yrs of my life and looks are an important part of that...dont want it to b but its tru and a good wieght for me would b about 129 according to my doctor... so my ? lol finally is how can i do that?? i need to loose about 40 pounds over the summer (i know its less than 129 but i want a little room in case i dont make it or in case i gain some bak) soo please help me im willing to work out (no other way really) im about to talk to my parents about joining a gym so i mostly wanna loose the weight around my stomach so a workout plan and a diet to follow that would help me to this goal would b amazing!!!!! pleaeee pleese help me!!! i really want this to work out