I have noticed that most of the posting members on this thread are moms, not dads. There is something significant in this fact, and I just want to post a word of warning mixed with encouragement.
I write as a father of a son going through puberty, as a former teenage boy, and as a pastor who works closely with teenage and college age young men.
Moms, please understand that your son is going through a massive physical and emotional transformation. His body is adjusting to manhood even as a flood of hormones is changing his life day by day. Testosterone is a main factor here, as his gonads are developing into reproductive machines and he is dealing with the massive energy of sexual arousal, etc. For a boy at puberty, this is a powerful challenge in itself. For a Christian boy, the struggle is especially hard, because he knows that he is not to give himself to sexual promiscuity, pornography, etc.--even as the world draws him in another direction.
His body is changing in other ways as well. Though you may notice his appetite and his proudly developing mustache and underarm hair, he is dealing with the enlargement of major muscles, the lengthening of his limbs, and the awkwardness of movement that comes with all this. Beyond these factors, testosterone and other hormones also fuel an aggressiveness in him that is not always pretty, and may scare his mother to death.
Here's my advice: Give him a good bit of room to handle these challenges. Don't smother him with motherly concern, but make sure he knows how much you love him--and how proud you are of how he is developing. Don't embarrass him by pointing constantly to his changing body, much less by making comments about his budding sexuality. Talk about your hopes for what he will be as a man, and make him feel big in your eyes. Give him more and more responsibility around the house, and let him do lots of outdoor work that makes use of his energy and need for exercise. Let him take out his aggression on leaves, the trash, and the lawn. Tell him you are proud of his strength, and encourage him to grow up to be a faithful husband and father.
BUT--Don't let him show disrespect to you. That is unacceptable under any circumstances. Put severe consequences in place for disrespect, and never waver in your determination to hold him accountable.
Furthermore, I must say that the situation is more complex for moms raising sons alone. Dad should take the lead in guiding his son to manhood, exercising discipline, serving as mentor, coach, teacher, and protector. Dad will need to discipline the son into showing respect for the mother. A boy at puberty is straining toward manhood in an awkward and clumsy way, and he cannot be allowed to disobey or disrespect mom. Ultimately, the son will obey mom because the dad makes it mandatory, in no uncertain terms. Dad also needs to be the guide through puberty and sexual development, dealing with everything from hygiene and grooming to wet dreams, erections, lust, and masturbation. That's hard for mom to deal with, and hard for a boy to hear from a woman--especially his mom.
If mom is alone--may God bless you--I pray that He will give you strength to bear your son through this time, giving you strength and sensitivity to deal with the son you so dearly love, but sometimes now do not understand. Can you find a good Christian man to help? In any event, may God be unto your son "the Father of the fatherless." By the grace of God, you and your son will both get through this. If you look hard enough, you will find great opportunities for laughter [as well as raised eyebrows] along the way.
Sincerely,
HonorTruth