It seems like many will argue until the end of time about what is the best theory to use when designing a workout. I feel however, that for most, a periodized workout is the best for optimizing strength gains and avoiding over training. Periodization is the gradual cycling of specificity, intensity, and volume of training to achieve peak levels of strength. The cycle will shift gradually from high volume and low intensity to low volume high intensity over several weeks. The length of the cycle revolves around the dates of competition. The typical powerlifting cycle will consist of three phases: Hypertrophy, strength, and power.  

The first phase is the hypertrophy phase, it will normally consist of eight to ten repetitions per set. This phase may last from one to six weeks with intensities from 65% to 79% of one repetition maximum ( 1 RM ). The hypertrophy phase is responsible for developing a good muscular and metabolic base for the future. All rest between sets in this phase should be kept between 45 seconds and 1.5 minutes. Shorter rests in this phase will maximize the natural primary anabolic hormones involved in muscle tissue growth such as testosterone, growth hormone, and insulinlike growth factors, while minimizing cortisol production.  

The second phase is called the strength phase, it will normally consist of five to eight repetitions per set. This phase may last from two to eight weeks. In the strength phase the weight intensity is gradually increased to loads of 80% to 90% of 1 RM. Obviously this is the phase where the athlete increases muscular strength. The rest between stets in the strength phase should be increased to about five minutes. This length of time will assure that the muscles have completely recovered from the higher intensity workout.  

The final phase of the powerlifting cycle is the power phase. This phase will consist of sets with repetitions of one to four and intensity levels gradually increasing from 90% to 107% of 1 RM. The power phase is where the athlete peaks the strength levels for competition. Rest between sets in the power phase should be increased to about five to ten minutes. These maximal to near maximal repetitions require much more time for the muscle to recover 100% and be ready for the next set.  

After the final phase is completed and the competition, if any, is over, it is usually best to take a week or two off. High intensity, single repetition work takes a lot out of the body and mind. Just taking a week or two out of the gym will give your body and mind time to completely recovery from the tremendous stress put on them in the power phase of the cycle. This rest can be active rest, where activities other than weight training can be done, or inactive rest.  

The following is a example of how one might set up a powerlifting cycle. I would emphasize that this routine is only a suggestion and by no means is the only periodized routine out there.   
  

Take your best and multiply it by the numbers given.  

2 reps - ? x 1.06   
3 reps - ? x 1.12   
4 reps - ? x 1.15   
5 reps - ? x 1.18  

This will give an estimate of your best 1 RM without actually having to do it. Now we have a number to work with.  

Warm ups  

Warm ups in powerlifting are only to get the body's core temperature up slightly to prepare for some serious lifting. DO NOT wear yourself out warming up. Use only four to five sets, low repetitions, and progressively heavier, LIGHT WEIGHT.  

This is an example of a warm up for someone who is squatting over 600 lbs.:  

135 - 1 set of 10 repetitions   
225 - 1 set of 5 repetitions   
315 - 1 set of 3 repetitions   
405 - 1 set of 1 repetition   
495 - 1 set of 1 repetition  

Get the idea?  

One other hint, this is not bodybuilding, so throw out anything you know about bodybuilding, it doesn't apply here.  

Work Sets  

This is where you get strong. Here, as we will discuss later, is where rest between sets is very important! In order for the energy levels in the body to return to 100%, sometimes three to ten minutes rest between the work sets is necessary. So TAKE YOUR TIME. I strongly believe two high intensity sets are all you need. Remember, INTENSITY is the key to strength, NOT VOLUME. Again, we are not trying to be a bodybuilder in powerlifting. With two sets you can work at 120%, without having to conserve any strength for that third or fourth or fifth set.  

Remember -- multiply your best 1 RM times the given percentage.  

Week 1 - 70% x 2 sets of 10 repetitions   
Week 2 - 70% x 2 sets of 10 repetitions   
Week 3 - 73% x 2 sets of 8 repetitions   
Week 4 - 76% x 2 sets of 8 repetitions   
Week 5 - 79% x 2 sets of 5 repetitions   
Week 6 - 82% x 2 sets of 5 repetitions   
Week 7 - 85% x 2 sets of 5 repetitions   
Week 8 - 88% x 2 sets of 5 repetitions   
Week 9 - 91% x 2 sets of 3 repetitions   
Week 10 - 94% x 2 sets of 3 repetitions   
Week 11 - 97% x 2 sets of 2 repetitions   
Week 12 - 100% x 2 set of 2 repetitions   
Week 13 - 104% x 1 set of 1 repetition   
Week 14 - 107% - 111% x 1 set of 1 repetition  

Now you have a 1 RM that can be used for the next cycle! You can add 7% to 11% every 12 weeks. With consistency, this amount of weight will add up to really big weight, in time. So be patient and consistent. DO NOT BE AFRAID TO ADD MORE WEIGHT TO THESE PERCENTAGES IF NEEDED. I can give you a plan to get strong, but you are the one who has to load up the bar. Don't cheat yourself.