I used to wait until I had a dense bush on my hands then start slow with taking the oldest fans and then only removing anything over a bud site.
I just started following the way Hashmaster does it - take fully formed fans as long as the next node has a set of fully formed fans to take on the photosynthetic load. It's a bit aggressive, I took the cotyledons and first finger leaves at 14 days then continuing with Hashmasters way. I tend to stop around having 3 fat fans at the top of each cola. The stress put on the plant causes the lower/side branches to increase in size and yield in an attempt to carry the plants photosynthetic load.
Defoliating isn't good for all plants, some produce less fans than others. I will also only defoliate healthy plants and allow the plant to recover after each plucking.