Scrogging and topping

If you have a small plant on its second set of leaves, and you are planning to scrog, when should you top. Read all about scrogging, and know I should start a little before flowering, but when do I top the plant if at all I have to?

I'm not a scrogger but I do train..read somewhere that you chop above the second or third node when topping. either that or when you get your first alternating node

id wait til week 4 or 5... just me.. ive heard 80000000 different ways that everyone has heard of but never really done themselves... i like week 5 personally bc i like my plants about 18-24 inches tall..some seem to make it there faster than others, but i wait til theyre the same height... even if one takes an extra week to get there.