One of the more common mistakes many new trainees make is to do too many exercises in a given workout. This is sometimes due to misinformation from the muscle mags or from junk posted on the Internet - you know, the type of routines that purpotedly take 3-4 hours daily to complete, include just about every exercise under the sun and then some (except the good ones) and put plenty of emphasis on "pumping and toning".
And sometimes, it's not even that - you'll find a beginner raring to go with GOOD exercises. He'll read about all the different types of good exercises he can do, and he'll start working them - but trouble is, a lot of times, he ends up trying to get good at ALL of them - at the same time. And this usually leads to frustration as he's attempting something that isn't easily done (unless you spend your entire day training, and even then it's tough to improve on tons of exercises at the same time). This leads to frustration, the trainee stops getting the results he'd like from his routine, gets disillusioned with it, and may end up dropping it altogether. Not good.
It's more common than you'd think, and yet, it's easily avoided by keeping this one maxim in your mind "One thing at a time, partner" (pardner, if you so choose).
Remember that it's ALWAYS better to pick a HANDFUL of exercises, and literally grind your body into the dust trying to get better at them, than picking 50 exercises and moving from one to the other without really improving on any of them. If your doing things right, and giving it your all, then it should be impossible for you to focus fully on - and make good progress in - more than a handful of exercises.
For instance, I focused on JUST pushups and pullups for my upper body routine this morning. That's it - no dips, no supplementary exercises I often do - just pushups and pullups. And my shoulders, chest and forearms feel like they're about to explode - at one point, I was doing good just to make it past a set of pushups and move on to the pull ups.
And I'm not saying not to try new things - not at all. Once you get good at a certain exercise, by all means try another one and get good at that as well - that's what I do myself. But the thing to avoid is "flitting from exercise to exercise without getting good at any of them" - do so, and you'll make great gains.
And just so you know, this is just as applicable to advanced trainees as it is to those that are just starting out. It doesn't matter if you can bang out 500 pushups per workout, or if you max out at 50 - the advice is just as applicable. Focus on ONE thing at a time for a given workout, and literally work that exercise (and your body) into the ground.
Incorporate this bit of advice into your training, and watch your results go through the roof in very little time.
PS: For more shoulder popping workouts, Fast and Furious Fitness is what you need to be focusing on.