@yahleel I start working on a variation when I can do between 5-6 reps, best way is to begin with some reps in reserve (2 or 3 reps minus your máx), so, lets say my máx is 6, begin with 3x4, then next week 3x5, next 3x6, next 3x7, now your máx is much more than 6, you can take a deload and retest your máx, If my new máx is 12+ then I change to a harder variation.
In your case for pullups I would follow something like this, considering your máx is 10 reps:
week 1: 3x7 (2x/week)
week 2: 3x8 (2x/week)
week 3: 3x9 (2x/week)
week 4: 3x10 (2x/week)
week 5: Deload and test your new máx