Back is like shoulders: always seen, unbelievably hot when rippling through a shirt, but very neglected. Don't neglect your back. And don't limit your back work to the typical garden variety pull-downs and rows.
When doing back, as with the other movements, practice with very light weights first. There are literally thousands of ways to hold and move the bar/dumbell with back work, so you really need to practice and figure out the best hand positions, etc. for you. Then over time, use a variety of hand positions (ones that work for you) to introduce variety to your routine and keep your muscles confused.
Work your upper back a lot. You've probably been taught to do rows with your hands low to hit your lats. This is true, but not all you should do. You should also incorporate rows with your hands high on your chest and elbows out (again, practice this movement to figure out how you should position your arms). The goal (think about this while practicing) is to hit the area between your shoulders, and covering your scapula. This will also indirectly hit your rear deltoids (see shoulders in Part 2).
Everyone loves to work their arms. Please do not neglect your other parts in the interest of your biceps. You look so much more "complete", and hot, with your body parts in proportion to each other. Most guys won't be able to say exactly why another guys physique looks off, but a lot of times, bad proportions is why.
Most guys don't have the best "muscle insertions". It's genetic and cannot be changed. But sometimes you can cover it up a bit. Your bicep muscles "insert" into your forearm. The longer the tendon, the bigger the gap between your bicep muscle and your forearm bone. That's "muscle insertion". If you have a really short tendon (and thereby long bicep muscles) it looks better.
To help cover up a long tendon or, in other words, a short bicep, you can work your forearm. To do this, when doing curls, do them with your hand facing down towards the floor. Or do "hammer curls": dumbell curls with your thumb facing upwards towards the ceiling. (The added benefit of doing curls this way is that it will hit your brachialis another one of those muscles no one hits, but when worked, will make your physique look that much more sexy...and your arms bigger too!)
As the top/outer part of your forearm grows, it will help fill in the space between your forearm bone and bicep muscles. It'll help hide the gap a bit.