This is very simple so no need to overcomplicate. Say you want to work up to a 3RM. Start with the bar, do 3 reps (or maybe a few more if you feel like it). Throw on some more weight, do 3 reps. Throw on some more weight, do 3 reps. The bar starts to get kinda heavy so you start making smaller jumps. You finally get to a set that is pretty damn hard.
At that point you make a decision on what you want to go for on that day and you throw that weight on there for your last set and go get it. If you still have some juice left you can go up again (if you underestimated) or take a little weight off and do one more set.
It is pretty much as easy as that, just do progressively heavier sets of three. After doing it once or twice you know about what you're going to work up to and you'll figure it out.
For a practical example, here's how you might work up to 225 x 3.
Bar x 5
95 x 5
135 x 3
165 x 3
195 x 3
215 x 3
225 x 3
and then at that point you can either:
1.) Go for 230 or 235 or even a 1 rep-max if you are feeling great.
2.) Do another set at say 215 or 205 if 225 was your best effort but you still have some more left in you.
3.) Go on to your assistance stuff if 225 really drained you.