Solid answer

Gotta turn gay if you wanna make any progress

this... and stretch a lot... flexibility is key to this stuff, pull a calf muscle during a flip = death

I dont know what kind of shape your in, but you really need to focus on your body. Like the guy said earlier gymnastics will help as far as the flips and stunts of parkour and then will also help you use your body weight and distribute it properly. Do a lot of pull ups!! If you can't do pull ups then you cant control your weight. If you can't do that that then your probably going to snap some S*IT up man.

I heard this works well.

useless

Be careful about the gym, most people train for strength there which won't help as much as other training.

You need flexibility and control. Strength helps but big muscles impede your movement. Martial arts would be best for honing all of these things.

Practice doing simple stuff like underbar. Search some youtube videos they will have good tutorials for beginners.

One other thing that helps is if you can join a gymnastics or breakdance club(or parkour club if they have one obv). There are a lot of similar skillsets here and even if you don't wanna do what they are doing you'll be able to use their facility to train.

to master the art of parkour you must break each bone atleast 25 times

Instead of parkour, me n my friends just fap all over town. Doesn't take as much athleticism, but you get to see the city in ways you never thought possible.

also

Have you tried Parkour Phenom for Kinect? It'll probably help you learn, just like how Gran Turismo taught me how to drive thru slaloms n chicanes n shit.