Autoregulation means that the amount of work you perform in a training session is adjusted on a daily basis depending on your capacity. It also implies that the method of training provides a "built-in" mechanism that automatically adjust the amount of work you are doing.
For example, when we use the "ramping" method, both the volume and training weight will automatically "select themselves" since you simply work up gradually to the max weight you can lift in solid form for the selected number of reps. If you are in good shape on a day you will be able to reach a higher end point, which means that your volume and training load will be high.
On a day where you "don't have it" you will not be able to work up as high so the volume and load will be automatically decreased.
Another good method is called "Giant Clusters". It really was how Egyptian olympic lifters trained back in the 30s and 40s, when they were among the strongest in the world believe it or not... Khadr El Touni an Egyptian lifter was the strongest olympic lifter pound for pound in the history of OL from 1936 up to 1996 when Suleymanoglu surpassed him.
It was also used by Ladislav Pataki, a strength scientist and competitive athlete (throws) from Czechoslovakia (who then moved to the US).
With this method the specific training weight, reps AND the training time for an exercise were selected before the workout.
Then the lifter had to do as many sets of the prescribed number of reps with the selected weight within the given time zone.
It was a training method later adopted by Canadian olympic lifting coach Pierre Roy.
The time zones should be 10, 15 and 20 minutes. 20 is for primary lifts only (one per day, most important movement), 15 minutes for the secondary movement and 10 for the 1-3 remedial exercises.
The rep selection would be either 6 (mostly for size, what Pierre called "olympic lifting-specific bodybuilding), 3 (the most often used number) and 1 (to work only on strength).
The load selection was roughly 2 reps below the RM. For example when doing sets of 6 you would use a weight that you can do 8 times; when doing sets of 3 you use a weight that you can lift 5 times; when doing sets of 1 you use a weight that you can lift 3 times.
The goal is to do as many sets as possible within the given time frame BUT you are only allowed ONE "less than perfect" rep (meaning one rep that doesn't go up strong and solid... if you grind it up, it is less than perfect).
So rest only as long as needed to be able to perform well.
You might mis-select your amount of rest between two sets and that would result in a bad rep. This is why I give you the right to do ONE less than perfect rep... in case you misevaluated your need for rest. A less than perfect rep is either due to accumulated fatigue or not enough rest. If it's the former, you stop the exercise, if it's the later simply rest a bit more.
So if you have one less than perfect rep during a set; do another set but with more rest to see if the problem was simply not resting enough. If the next set is solid than you can continue. If you miss another rep during that set the problem is cumulative fatigue and you should stop the exercise.
REALLY try to finish the time zone. BUT if you have two less than perfect reps, stop.
So an exercise is either terminated when the time is up OR if you do 2 less than perfect reps.