What behavioral changes can I expect during adolescence?
On a practical level, you'll find yourself more clumsy because you are constantly having to adjust to a different size body.
You'll be more moody. That is, your moods will become more extreme and change suddenly. You'll suddenly feel like crying over something that a few years ago would only annoy you. You might get really angry over small matters. When you are happy, you will bounce around. So keep in mind that your feelings will not always be reliable.
One of the big things to remember is that teenagers are not able to read facial expressions and body language well. They have a tendency to assign too extreme of emotion to what is actually being portrayed. It is due to the brain rewiring itself for adult thinking. Just don't assume you know what someone is thinking because of the way you see them act.
Adolescent males also tend to take risks. The part of the brain that handles judgment in regards to risk assessment doesn't fully develop until your mid-twenties. What happens is that you will get ideas that seem to be a good idea, but you won't think about all the possible consequences, and thus, the result is doing thing that in hindsight you realize was really stupid.