I learned these things the hard way. Maybe you won’t have to.

• Don’t shave!
  It may come naturally to you after a morning workout. You take a shower, then you’ll want to shave, since your hair’s been softened by the hot water. Don’t do it! There’s still plenty of blood right under your skin, thanks to the workout, and your hand muscles, having just lifted heavy weights, will inadvertently exert too much pressure on the skin. These two things will translate into cuts, cuts and more cuts… unless your face is tougher than treated leather.
• Don’t eat right away.
  Allow your body to relax a bit, for at least 30-60 minutes. You may be tempted to drink a shake, or dig into a steak, wanting to get some proteins and carbs into your body, but it’s not a good idea. You’ve just lifted heavy things or done some strenuous cardio, and your body is still racing. It needs time to relax and get back to normal before you can eat and digest food properly.
• Don’t go outside in cold weather.
  Sure, you may think you’re tough, because you’ve just bested yourself at the deadlift, leg press or bench press, but if you’ve broken out in sweat, and then you go outside in your workout clothes, or right after a shower, thinking you’ll be just fine for a few minutes, you may discover pneumonia couldn’t care less about your fitness level. Dry yourself thoroughly, get dressed properly, and then head outside.