Getting a concussion isn't easy for everyone.
For me it's like riding a bike, for others it's like landing on the moon.
You have to be passionate about getting one, if don't you will never get one.
So If you haven't had one yet, and wants to get one. I will recommend you to
hit your head really hard, into a brick wall or a pole and such.
That's what's most effective.
When I get a concussion, it is always to get out of something.
Such as school, training and events.
I really think that concussions is one of the most beautiful things in life.
The feeling you get of having one, is amazing.
You feel this good dizziness inside your head, and you get all relaxed.
It is literally the best feeling in the world. 
So if you want to get high without smoking weed, or you have to go somewhere or do something, that you don't want to do.

Just get a concussion.