I know the first thing you think is Lifting weights but i am in high school and I am 6'3' so i am a big man, but everyone else i play against is my hight, but weighing like 180. I weigh 156, so it is naturally hard for me to post them up, be cause they just easily push me out no matter how hard i try.
*I am a shooter, but since i am the tallest, i have to be a post player.
First off...there are some guys out there that should provide some inspiration to a skinny post player....Kevin Garnett comes to mind. It is possible to be effective in the post.
That said, here are some things to keep in mind.
In the short term:
Use your quickness and length. I assume you are quicker than the bigger guys. If you are quick, than you can use footwork to be effective post defender. Use that quickness to front the post if they are deep, beat them to spots (if the ball is swung around the perimeter, you have to bear them across the paint), keep your feet moving to get around them. When they do have the ball, sometimes bigger guys will try to lower their shoulder to out-muscle you, if they lower that shoulder, you can take a charge. You can also tire them out by making them chase you on defense. If you sprint the floor hard all game, you should be able to wear them down. Additionally, if you are taller than them...use your length to bother their shot.
In the longer term:
You should work on building your size and strength....this is done by a combination of nutrition and lifting. You want to make sure you are getting enough calories...especially from healthy fats and proteins. You should be getting plenty of protein (.7 - 1.0 grams per pound of bodyweight). It is okay to add in some supplements. You also need to be getting healthy fats from things like almonds, walnuts, pecans, olive oil, coconut oil, avocado etc...
Post workout nutrition is important...protein and carbohydrates withing 30-45 minutes of finishing up your workout. Stick with steak/chicken/fish + sweet potato (awesome post-workout carb) and some other vegetables.
Since you are on the lighter side...an extra protein shake with whole milk would be a good daily supplement. You are always probably playing and working out a lot...so you are going to need more calories than an average 17 year old kid....so make sure you are eating enough...you need to put ON weight. If you are hungry eat....just try to avoid pizza, candy bars, chocolate, etc...
In terms of the lifting. Basketball strength training needs to create players that are explosive, so you want to build Fast-twitch muscle fibers. This is done through heavy and explosive lifts. Some of the best lifts for basketball players are: bulgarian split squats, back squats, deadlifts, power cleans, glute-ham raises, glute-ham sit-ups, squat thrusts...plus you should be getting in a lot of stuff that deals with strength to bodyweight ratios: pull-ups, push-ups, squat jumps, dips....and finally some plyos for speed/agility/jumping (box jumps, weighted box jumps, box jumps with the ball overhead.
You should also work on improving your foot-speed and defensive technique. This will serve you well as you play against bigger players. Head to this site: Basketball Training at WOH
for more information, drills, videos, etc...
One more thing...don't forget about the other skills. If you want to play at the next level (college). You will again become a 2 or a 3 man. Make sure you are continually refining your handle and shooting in the off season.
Hit me up if you want to discuss an individual training program: firstname.lastname@example.org