Pruning

I'm wondering at what stage should I prune as well as how far down???

I prune after the stretch in flower.

I top, pinch and tie down branches to get a wide, short plant with many bud sites and an even canopy. If there are any left that are obstructed by more productive upper branches I prune them. I also remove a lot of big mature fan leaves to get better light penetration to as many bud sites as I can. This also opens up the plants and allows for good air circulation.

You only need to do it once. Waiting until after the stretch gives you an idea of how the branches are going to be oriented for the rest of flowering.

I have accidentally "pruned" branches later in flowering trying to tie them down. Didnt seem to bother the plant.

I thought it was better to prune in the early stages to allow the plant to develop before flower???

Or does it really matter when you prune as long as its done?