Whereas the movement of a girl into puberty would be continuous and smooth, for a boy, it is more in spurts, and so in between these spurts it may be easy to miss out that they too are going through changes. Inform yourself first as it is important to understand the range of things that happen, before you talk to your son.
After that, the following points need to be looked at:
Bodily changes: First and foremost are the changes that you need to talk about. Inform them that their voice might break as they grow an adult male voice, about facial hair and shaving, as well as secondary sexual characteristics like pubic hair. Tell them that the hormonal changes that lead to all this will also make them more volatile in mood make them see girls differently and may lead to instant liking and disliking of people and things. Tell them to not act on impulses as far as possible.
Increase in aggression: As testosterone levels change in the body to help out make the necessary changes for the boy to become a man, it may also need to aggressive tendencies. First tell yourself and then your son that this is normal. If you expect it and normalize, it is easier to handle. Expect some anger, some rage. Make sure you keep talking to your son in an understanding manner so they don’t feel bottled up. Further, direct the aggression towards constructive activities like sports to ease it out.
Hygiene and care: You need to tell them how to clean up after a wet dream as well as the importance of maintaining general hygiene in the private parts, including shaving regularly. Masturbation is a healthy and good release, but needs to be hygienic. Help them with information, privacy and an understanding attitude at this point.
Exchange of adult material: At this age, boys tend to exchange pornographic material. This is overhyped and unrealistic and can misinform them about sex. Tell them that this will happen and if they want actual information about the sexual act, it is better to see proper information sources. Do not deny this information to them as they are naturally curious and its better they satisfy the curiosity with the right information than the wrong one. At the same time, talk to them about waiting to grow up before they act on any of this information. Coming from a person who wants them to know the right things, they will listen to you when you ask them to wait.
Peer pressure for certain activities: There might be peer pressure to try out smoking, drinking, drugs, late nights and reckless activity. Tell them beforehand that other boys may pressurize them into this, but not to fall in the trap as this will derail them from their life goals. Tell them they can have healthy fun like music concerts and going out to eat but not beyond that. Be a friend to them and empathize with them and they will surely listen to you.