
An important, but often neglected step in creating a custom workout plan involves choosing a progression plan. Progression, also called progressive overload, is the addition of weight over time.
Progression begins on the set level, with the addition of reps. Eventually when we are capable of performing a quality number of reps per set, we add weight to make the set more challenging once again.
Progressive overload is the fuel that drives muscle gains. Without progression, or the addition of weight over time, you won't see much in the way of muscle gains. While the muscle building process does not require you to train for absolute strength, it does require you to dramatically improve your strength above and beyond where it is now.
Remember this truth: no one with a substantial amount of muscle mass is weak. Focus on progressing in standard hypertrophy – muscle building – rep ranges. We will detail these ranges below.
It won't matter much how you progress, as long as you progress – so pick a set and rep scheme that appeals to you. For compound exercises it is best to stick with the 5-12 rep range the majority of the time. For isolation exercises, and some machine and cable exercises, you will find that the 8-15 rep range is a better fit.
Certain leg exercises such as leg press and squats can work well with higher rep schemes. If you do add in 15 or 20 rep sets of squats, it will be in your best interest to decrease the volume of sets a bit. Leg presses, on the other hand, aren't as taxing. If you bump your leg press reps up to 15-20 per set, you can keep the same number of sets.

Please note that you can use different progression schemes for different exercises. It is not necessary to pick only one progression scheme for compound exercises, and one for isolation exercises. With that said, be careful about over-complicating things.
On a final note, remember that rep ranges are only guidelines. It's ok to go a little higher or normal, based on how your body is performing on any given day with a weight. Just because a set calls for 8-12 reps doesn't mean you should stop at 12 if you are capable of doing more.
You should know that if you only hit 6 reps on a set that calls for 8-12 reps, it's not the end of the world. Remember, improvement (progression) is the magic, not specific rep ranges. Regardless of what reps you hit per set, try to improve the next time you work out.
There are 2 ways you can approach progression when working with the 8-12 rep range.
8x12 Method #1 - Stick with the same weight for each of the sets. When you reach 12 or more reps for your first set, add weight to this exercise the next time you hit the gym. Your third set may dip below 8 reps. That's ok. Remember progression is more important than rep ranges.
8x12 Method #2 – When you struggle to hit over 8 reps on a set, drop the next set's weight by 10%. So for example, Let's say you're using 185 pounds on the bench press and your first 2 sets look like this:
For the third set you decide to drop the weight by (about) 10%, and go use 165 pounds. This set may look something like this:
When you are able to reach 12 reps for set one, using your top weight, add the same amount of weight to set 3.

This scheme functions just like the 8-12 rep progression approach. You can choose to either use the same weight for each of the sets, or drop the weight 10% when you are struggling to hit 6 total reps.
Another progression approach that functions in the same way as the 8-12 rep scheme. 8-15 reps is a great choice for isolation exercises, as well as cable and machine lifts. You can also use this approach for squats and deadlifts. When you are able to perform 15 reps for your top set, add weight the next time you use this exercise.
5x5 schemes are extremely popular, and have been for many decades. They are perfect for the heaviest of compound exercises: squats, deadlifts, bench press, overhead press and barbell rows. Your 5 sets will be performed as follows:
Your last 3 sets are your “money sets.” When you are able to perform 5 reps on your last set without grinding it out, and with good form, add 5 pounds the next time you perform this lift. The weight you use for sets 1 and 2 are percentages, based on your set 3-5 weight. This means that if you are using 200 pounds for your last 3 sets, your 5 set scheme would look like this:

Note: You may also use the 4-6 rep range for your first set. Start with a weight that allows 6 reps. For set two, drop the weight 5-10% and perform as many reps as possible. Drop another 5-10% for sets 3 (and 4, if you are using 4 sets). When you are able to perform 8 or more reps for set one, add weight to each of the sets. For example, let's say you are using 200 pounds on the bench press are are able to perform 8 reps for your first set:
Because you reached 8 reps for your first set, you will add 5 pounds to each of your sets the next time you bench.
Start with a weight that allows 12 reps. For set two, increase the weight 5-10% and perform as many reps as possible. Add another 5-10% for set 3 (and 4, if you are using 4 sets). When you are able to perform 15 or more reps for set one, add weight to each of the sets. For example, let's say you are using 150 pounds on the bench press and are able to perform 15 reps for your first set:
Because you reached 15 reps for your first set, you will add 5 pounds to each of your sets the next time you bench.
All of the progression schemes above can be modified to fit your specific needs. For isolation exercises, or sets within the 8-15 rep range, you simply shift your goals up slightly.
For example: if you decide to use 10-15 reps for calf raises, you could add weight when you are able to reach 15 reps on your first set. You could also use the 10-20 rep range, and add weight when you reach 20 reps. There are many possibilities.