Well, I'm not an expert and I got started in boxing because I enjoyed watching fights. A couple of basic rules
1. Allways keep your hands up, covering the area between your ear and your chin. If your right handed, your right hand stays up and you can bring your left hand out, maybe 6 inches away from your face. If left handed, do the opposite. When you are close enough to smell his breath, keep both hands close to the face.
2. Tuck your chin and look up and out as if you were looking through your eyebrows. Exposed chin is bad. Keep your eyes on your opponents chest/shoulders, not on his hands. Learn to read his body.
3. Your punching power comes from the push off from your legs and rotation of the hips, not just your arms. Punch with your entire body.
4. When throwing punches make sure your head stays between your feet and that you're not leaning your head out. Punch power comes from the lower third of your body.
5. Your stance/body should be poised, not tense and flexed like a bodybuilder but not loose like a wet noodle.
6. When punching, allways make sure that the other hand is up and covering your cheek/jaw.
7. Go to a boxing gym. Talk to some fighters. Find a coach and just have fun with it. Some people will be intense and serious and some people will be laid back.