im on my first grow, i have 2 seperate cabs, one has 4x diesel ryder autoflowering dwarfs, and the other has 1x skunk #1 (fem) and 1x thai superskunk.
im my main cab i have 2x diesel ryders at 6 weeks old, and i let them grow normaly for 3 weeks then i slowly stretched the lower branches out farther and farther to get more light on the lower buds, this has doubled my plants size in 3 weeks ( both bigger ones) and i have one that i have been lst'ing since 1. 1/2 weeks old and it is growing awesome and showed signs of sex at 2weeks.
in my seperate cab i have a skunk #1 that i ahve done nothing to at all, and a thai superskunk seed, the thai was 5 inches @ 1 weeks old, so i trimmed her up a bit and started stretching ( with very very good results, 9 nodes), from my experience so far as a noob i would say that you could start lst'ing whenever you feel like it is time, just do a little bit of research before hand.