Whether or not you carry around a bit of extra baggage like most men, overall strength and physical health can make your quality of life orders of magnitude better (sex, confidence, desirability, getting around, etc). As well, beginners and experienced gym goers are both always learning, and the pros can only write so much in the magazines and online. This post is intended to share several specific points the pros have learned over their decades of gym work.
Beginners and seasoned gym goers alike, take a step back and practice your movements. Have you ever played baseball or golf? What was the first thing your coach taught you about hitting the ball? Just make contact, do not try and kill it.The same goes for every movement in the gym.
Next time you are at the gym, before you start your bench press, curls, or crunches, practice the movement. This means, for example, doing your first set of bench press with an empty bar. Or, dumbell curls with 5lbs. The only purpose is to let you discover what angles are the best for you. Even if you've been going to the gym for decades, this is a great experience that will help you refine your craft.
Perform the movement in a variety of ways until you find which way causes your muscles to be affected the most. For a curl, change the angle of your hand, the angle of your arm from your body, the max and min distance that you move the dumbell, etc.
Once you've discovered the best combination, practice it many times so it becomes automatic. Many times means over many gym sessions. It needs to become habit that you're always striving for the best way to hit your muscle.
Once it's automatic, you can increase the weight. Just remember, this is exactly how you learn to hit a baseball or golf ball. You have to do this with every movement in the gym (machines too!).
When practicing, and in your final movements, make sure to squeeze at the end. What does "squeeze" really mean? Have you ever flexed a muscle so hard that it cramped and hurt like hell and kind of "stuck" flexed until your panicked from the pain and pulled out of it? Think of that.
You don't want to get into the cramp and perma-flexed position, but you do want to get into the state right before that happens. It takes some practice (again, this goes back to practicing each movement) to figure out where that threshold is.