Weightage Up:

1. Work to your "Day max" (Day Max=Maximum you can do for that day). It could be a 1RM,2RM,3RM

2. If it's a day 1RM, you could try hitting a few more singles at that weight. Maybe 4-5 sets of singles. Same works with the other rep ranges.

3. My max strength session usually looks like this;

20KG x 6-10
40KG x 5
60KG x 4
80KG x 3
100KG x 3
110KG x 3
120KG x 3
130KG x 3
140KG x 2
145KG x 1
150KG x 1

This is the important part

I choose either 120-130-140KG's to squat for the next few important sets. IF I feel like shit, I'll go 120KG. Sometimes even 110KG.
If I feel good, I'll take a higher weight. Lets say I've an average day. I'll do;

130KG x 5 x 3-4 reps

Here's the biggest thing you need to know about getting stronger in squats. And in almost every other compound exercise. The reps and sets. DO NOT matter. Now don't scream at me and say "The squatting gods said this that and that" I'm not even going to elaborate on this. Too many people will have different views. But let me just say, if you want to increase your numbers, you should INCREASE the numbers. If you can't increase the numbers, maintain the weight and keep banging out the repetitions and sets. If you could do 4 last week, and 5 this week, you've improved. Dont' be too caught up in high rep low rep bull.