Add weight on sets 2 and 4; set 3 is somewhere between sets 1 and 2. If you look at what your predicted 1RM is for each set, the loads should show a fairly steady increase across the board. Check out this thread:
Wave loading and 1RM (WFS).
That thread came up just as I was planning to do Strength-I, and to me it seemed like a pretty logical way to plan the weights. So, I designed a spreadsheet using the formula
1RM = weight * 36 / (37-reps) to help choose the weights for each set. You can see what it looks like and the results I got in my workout log under Strength I.