If you want to get the most from your workouts, it helps to have a good understanding of how the muscle functions... It's bio-mechanical function and anatomy. The Biceps are a great example. Understanding the lever principal will help in making sure you are working the muscle that you intend to work during an exercise.
For instance. If you've ever wondered why it's beneficial to make sure that you supinate (have palms facing up) your grip when working biceps, It is important to know that the bicep muscle crosses over the elbow joint and inserts into the radius bone. the radius is one of the 2 bones in the forearm. It is the one on the thumb side. when you twist your hand like you are opening a door the radius radiates AROUND the ulna. If you watch your bicep you will see that is flexes when you supinate your palm by turning your palms up and thumbs away from the body.
Another neat bit of information is that the bicep crosses over the shoulder joint and actually originates from the top inside of the scapula (shoulder blade).
Knowing this information will help you on arm day to focus on getting the best contractions possible. the Idea is to shorten the muscle as much as possible right? Well, if this is the case an actual bicep curl may need to end by bringing the elbows in front of the body and upwards. This would shorten the muscle more by bringing the origin and insertion points closer together.
Other great exercises are close grip pull downs (palms facing you) and chins (pull ups with palms facing you and about 6-8 inches to shoulders width apart.
So, experiment with cables, dumb bells, bar bells and various positions to get the most out of your workouts... And have fun building those guns.
Strength, Courage and Honor!