Some people in here are trying to make progression for squatting. An important factor is knowing how your form is.
As faggy as it may sound, film your heavy sets once in a while. or film the last of a 5x5 set. You'll know how those knee's are doing in comparison to the toe's, how deep you are going, how the knee's position horizontally, if you are bending over to much, etc.
Today i had my last set of a 5x3 filmed. You felt each rep while doing it, got an idea of wether you were doing it right or not, and now you can see how you did, and compare the feeling you had during the set, how it actually looks.
From this, you can learn better while doing sets, how its looking like. was it a bad rep or not ? you have a better idea now.
In the last set, i got confirmed my first rep was good, the second was more decent then i tought, and the third had as bad form as i tought, but its the final rep of the series so thats to be expected.
For people that squat and deadlift with "dem heavy ass weights", its a really good help, try it !