DO NOT start now.
pruning, topping, low stress training, FIM etc. are a variety of techniques that work best to your advantage in veg from week 3 onwards.

its best to STOP pruning in veg 10-15 days before starting flowering. this allows time for plant to heal and relax from the stress put on it.
manipulating a plants growth requires that plant to use energy to repair fresh cuts.
you want your plant to focus on nothing but flowering when in flower.

if size is an issue. gently tie down flexible new growth. use a tomato cage if thats convenient for you.

lots of info out here from more experienced people then myself. LOTS and LOTS of info and pics.