Distance off the net
While the biggest timing factor is the hitter’s jump, you need to adjust your block jump based on how far off the net the hitter will be attacking the ball. The further back, the more you must wait to account for the longer time it will take for the ball to reach you. A back row attack, for example, requires a bit of a delay in your jump compared to a ball set tight to the net.
Speed of the hitter’s arm swing
The final little adjustment to timing comes by accounting for how hard the hitter attacks the ball. This is just like adjusting for the hitter’s distance off the net. An attacker with a fast arm swing will get the ball to you quicker than a player with a slow one. As a result, you have to delay a bit for the latter and jump a bit earlier for the former. If you can catch the hitter setting up an off-speed shot, that could also factor into your block timing (or your decision to go up at all).
Commit vs. Read
The jump, distance, and arm swing timing factors are going to be the same whether you are commit blocking (going up with a hitter without waiting to see if they are getting set) or reading blocking (waiting for the set). If you are commit blocking you still have to time your block based on the hitter’s jump, how near the net they are, and the speed of their swing.