This is something I've been working on for another project, and a quick n dirty paraphrase at that, but I figured it'd be a good thing to go on this site considering the insane n00b factor here.
A muscle grows when it is exposed to a tension that is above and beyond what it is capable of handling.
Tension is more than simply weight on the bar. It's also how that weight is applied, via biomechanics, and how that tension is generated.
This means, in laymans terms, that you won't be doing barbell curls for your legs and you won't be doing squats to help your pullups. Muscle specificity, in other words. This isn't a principle most people have trouble grasping, but it's here just in case.
How tension is generated is another more critical issue. There's three fundamental ways to increase tension in a muscle: maximal effort, repeated effort, and dynamic effort. For the purposes of growing a muscle, the repeated effort should be emphasized, although the other two certainly have a place. Note that this doesn't preclude other types of muscle action, such as isometrics and eccentrics.
The repeated effort method involves taking a weight to a maximum number of reps in the 5-10 rep range. Note that this does not necessarily mean grinding out reps to failure; leaving a rep or two in the tank is almost always advisable, but the growth stimulus in the repeated effort method comes from near the end of the set, when it becomes difficult.
There's a range of reps that are found to be optimal for hypertrophy. Classically, 1-5 reps are for strength, 4-6 reps are "intensive" hypertrophy, 5-10 reps are the hypertrophy "sweet spot, 12-15 are "extensive" hypertrophy, and 15+ reps are strength endurance.
As you can see, there's an overlap between a lot of the rep ranges, and this is where you'll find the use of other methods. For example, the maximal effort method can be used for intensive hypertrophy, where the two ranges overlap.
The gist of it is this: pick a handful of big exercises, so you're targeting a good portion of muscle, and work on them with sets in the 5-10 range. Push hard, but not necessarily to absolute need-a-spotter failure.
This is because the muscle sends a variety of biochemical signals to that kind of work, namely mechanical disruption of the fiber, that cause a drastic increase in protein synthesis. Since the contractile proteins of the muscle are what 1) comprise most of the muscle's volume and 2) make you stronger, this is desirable for pretty much everyone.
Contrary to what the muscle comics say, the pump isn't an indicator of growth or growth potential. The pump is an indicator that the muscle has been metabolically taxed, and thusly blood is flowing into it.
This can aid in growth assuming the conditions above are met, but does not signal growth in and of itself, certainly not to the same degree.
The pump is basically a depletion of the muscle fiber's energy stores, which causes a corresponding increase in the volume of those stores.
So, assuming you've hit the muscle hard with one or two big compound movements, you can then "finish" the muscle with a couple of sets of a "pumping" exercise. This will bring in blood and help with the metabolic adaptations, which do contribute to growth.
Putting It Into Practice
This isn't hard. Take a small part, like the chest:
Bench Press - 5x5, straight weight
Cable Flye - 2x15
Or something bigger, like the legs:
Squat - 5x5, straight weight
RDL/GM - 2-3x6-8
Leg Curl/Leg Extension - 1-2x12-15 each
You see where this is going. Pick a big exercise or two, work the hell out of them, then finish it up with higher-rep work.
A few bullet-point options:
- For the big exercise for a given part, you should center on repeated effort work, typically 4-6 sets of 5-10 reps. But you can also choose to occasionally do a maximal set of 5-10, or even dynamic work which would be 3-5 reps done for at least 5-6 sets, as fast as possible and with a lower percentage.
- The pump exercise should ideally be some foo-foo isolation work, stuff like flyes and leg curls and all that. Keep the reps over 12 on this stuff.
- A note on frequency. At a bare minimum, most parts should be worked every 5 days, and probably more than that. Smaller, faster-recovering parts, as well as exercises that detrain quickly, can likely benefit from even more than this. This doesn't mean, however, that you can train them to hell and still expect to grow.
- For volume, 25-50 reps per part per session is about the limit, and on big barbell movements like squats, benches, deads, all that, I'd limit it to 75-100 reps per week.