Understanding variations (and using them for a purpose). 

Here are some general rules:

- Closer to a comp (or max out) - more specific, less variation

- The purpose should always be to ASSIST the main lifts

- Anything other than a single in the big three is technically a variation

Almost all beginners don’t need variations, they need to practice the big three more. A lot of beginner gains are simply technical wins or better muscular activation. 

The only real variation you should need is rep range, and the big three should be in all programming.

Once you are more advanced, you generally use variations to lower the accumulation of stress on the body and work on weak points. Long blocks of 250kg on your back affect CNS and your shoulder joints whether you like it or not. A huge bonus is using variations to allow long blocks of linear progression on the weight.

A safety squat bar is a great example of getting work in without beating up the shoulders.

You could validly have no belt, no sleeve, pause a SSB squat for 10’s, in a non-competition cycle, and have a huge block of linear gains. Add weight each week until at 9RPE, add sleeves, continue, then add a belt, continue, remove pause, continue, back to 6 reps, continue.

That may not sound very exciting to a beginner, but intermediates and advanced that grind against the same weights all the time get very excited about a long linear block.