Read every cheap used Bodybuilding book you can find on amazon. Take em seriously. If you dont currently eat a meal with 30 grams of protein every 3-4 hours, then start. Bodybuilding starts with diet, and some say diet is more important than what you do in the gym.
Bodybuilders will do exercises strict, no matter how little weight is used. They will sacrifise looking strong to do a exercise strictly, and when they get better results than people using as much weight as they can, the other people will reconsider.
Dont get me wrong. I do like lifting more weight than other people, I do like some ego stuff, and I would have made a lot of better choices when I was your age if I could. Mainly those things. I started when I was 20.
For now thats what i got for ya. Take it seriously, don't plan on using anything besides protein for a while. Before you ever delve into what most of this forum is about, you gotta know how to get results. You gotta have the right workouts, learn how your body responds, etc.............
Otherwise you waste your freshest, purest hits and opportunities.
Finding your fitness goals, making decisions that will affect the rest of your life is important. You can get hooked on just about anything at your age. So good habits such as exercise is a good idea. For the record, yes you will get better results off of MJ although its a anti-oxidant and all that.
ANywho, you said bodybuilding. Bodybuilding is a lifestyle. For most, the eating is bizarre when it comes to family gatherings, restaurants, and bars. If your serious, really serious you wont waste emptiness and money on alcohol. Or at least not often.
But would I start this endeavor hard if I were you? You know it.
Also, I will note. I am nowhere near the best, and dont have the best tips for ya. You will find that no matter what you do, you cannot be the best bodybuilder. No matter what. Thats whats kinda cool. Because who is the best? The person who can bench 500 or the guy with the bigger chest?
The guy with abnormally large biceps, or the guy lifting the guy with the large bicep's car in the parkinglot with his teeth?
So, find out your goals. But also beaware. Bodybuilders arent flexible. Flexibility elongates muscles and is undesirable for bodybuilders. You can get too big to fit through small spaces, although you arent fat, just too big to get through a small space. It all depends on what you want.
You can get calves so big, they actually kinda look digusting and you might wanna hide em. Whereas some bodybuilder might wanna buy em off you.
So determining what kind of bodybuilder you wanna be is important. Do you for instance want to be careful on your knees so that you can walk when you are 75 years old. Then be careful squatting, dealifting, leg pressing, sprinting. What about rotator cuff and shoulder injury? Might wanna make absolute sure you do bench press in a way that has the least risk of rotator cuff or shoulder injury.
Some bodybuilders take huge risks on things, and you may wanna decide if f'in your knees up for life is worth some quads.
Just a few little things for younger peeps getting into this.
You will probably eventually get wrist problems of some sorts possibly. Another thing that many people get that cannot ever fully go away. There are things you can do to prevent though, and be careful of. Research it, and common causes of wrist injury and prevention. Learn the worst position to have your wrist in.
So, thats bout all I got for now on the things you might not be aware of, or looked at from this perspective.