As mentioned in This Post for myself the number 24 (3 sets of 8, 4 sets of 6, even 12 sets of 2 etc.) represents a perfect number in regard to optimizing exercise volume & intensity.
Frequency of training is another important component—especially for the natural trainee, and is determined ultimately by the aforementioned level of intensity.
There is a finite level of intensity that a trainee will reach before they see some regression. Sustaining upper-level intensity can only go on for so long.
In the past with my own training, I would almost always take each set to at least positive failure (sometimes beyond if I had a training partner or a spotter) and while this style of training certainly sends the brain signals to increase strength & size, it also can quickly and sometimes abruptly fry your CNS (Central Nervous System.)—possibly causing a plethora of negative outcomes (injury, illness, negative hormonal response etc.)
I used to judge a workout mainly on how sore I was the following day(s) but now am not so sure that soreness is indicative of progress at all.
For example I have been doing exactly three exercises for the last few months and am never sore despite making progress strength-wise on all three lifts.
If I were to say decide to throw some in some deadlifts into the mix, even though quite a few of the same muscles are utilized in squats that I train four times a week, I would probably wake up the next day with some minor soreness in the traps, but this soreness would be short-lived if I continued to perform deadlifts in the manner I am currently doing the dips, chin-ups & squats (high-frequency, low volume, progression through periodization.)
A popular notion in bodybuilding magazine workouts is to base training on specific body-part splits, hitting one area/part per day with extensive volume and oftentimes high intensity (i.e. Monday-Chest, Tuesday-Back, Wednesday-Legs, Thursday-Shoulders, Friday-Arms etc.)
While some have had success with this approach, I believe a better pathway to progress for natural trainees is to curtail the volume and increase the frequency in which you hit specific areas.
Full-Body Workouts (3 times per week.)
All of these, have you working specific areas with increased frequency and the programming for each is way more optimal for natural trainees in my opinion