I love topping my plants....I do it on all of them. While there are strains that do not respond very well to topping most of the ones I have seen do great with it.....I'm sure there are others that know better which strains don't top well. As for when to do it....it must be done before flowering and I usually leave a week (in hydro) for the growth to regenerate before I put them in 12/12 ...if you don't let the budsites grow back they won't be growing you any buds. I try to wait until the top node has about 1/2 inch stem then snip it right in the middle...too close to the bottom and you may clip off some future needed foliage. i'm sure there a folks here that have photos or diagrams posted on how to do it....I personally found that topping my plants increased the yield by a huge amount (using a strain that likes topping of course) KP mentioned on another thread "topping the tops" and that is basically what I do....makes for longer tiime in veg but happy days in flower