When to defoliate?

I have always defoliated right before I flip the switch for 12/12. By defoliation I mean a selective removal of any large fan leaves that are blocking light from potential bud sites. I don't mean a total stripping of the plant. I notice some people defoliate in the early stages of flowering and others not at all.

So what is the best thing to do here?

Most of the very bottom and/or inner fan leaves under thick canopy typically die anyway so may as well pinch those off. When lollipopping I also pull off any sizable bottom stems and they go str8 into the cloner. You don’t even have to defoliate at all but by taking off the leaf that would have shriveled up and died by week 6 anyway the plant can focus energy on the top most buds. Plus increasing airflow is always a good thing. You could also just pull off the dead shit as you go; up to you.

I try to do most of it during veg. But sometimes I'm lazy and don't do anything until 3 weeks in flower. But regardless I try to do all that before within the first few weeks. Some plants will stress out if you do too much, too late in flower.