When to start LST?

I started LST this grow when my plant was 5" tall (a dwarf strain) and 16 days old. Though for your first time, I would recommend waiting until your plant is 6-12" tall with 4-6 nodes. Week 3 is ideal, but even week 4 is good. LST is absolutely worth doing even on a dwarf strain. The "stress" is beneficial and its a free way to increase your yield. The only reason not to use LST would be if you're a more experienced grower looking to use another method of training that doesn't work with LST (most do). My first grow I began LST around Day 22 on a dwarf strain. LST kept it to about a foot tall (my first diary), and I defoliated because dwarf strains can become very bushy. This grow I started LST on day 16, defoliation in week 4, and will probably add super cropping in week 6 to further boost yield. To me this is one of the most enjoyable parts of growing.