How much should i lift when i lift

Question
I'm 12 y/o and weigh 190 lbs. i wondered how much i should lift and what i should do when i do lift.

Answer
lifting weights at your ages is tricky.  some say that its a good idea some disagree.  if its done correctly i think it can be a benefit.  if you were to begin a lifting program the first thing you have to remember is that your 12.  you're not done growing yet, you won't be for some years.  so its not important that you develop huge muscles, cuz it ain't gonna happen, yet.  but if you lift correctly it can reduce the risk of injury to your developing knees and elbows and other injury prone joints.  

with that being said, i'd say dumbells would be your best bet.  they work in two ways first, they're not very big/heavy.  the lifts that you should be doing you want to be able to do at least 12-15 reps per set.  so the weights that you use won't ever be that heavy.  if you start using weight that is too heavy for 12-15 reps, then you have to back it off.  lifting weights can help you out, but only if you do it properly, you don't want to hurt yourself while your lifting, that wouldn't help anyone. make sure that your parents or someone is there to look after you, don't ever lift weights by yourself.  so give it a try, be careful, and good luck!