Topping - Cutting off the top growth shoot on the main stem, this gives you 2 main cola's instead of one.

Fimming - Similar to topping but you leave 10-20% of the shoot, this should give several cola's

LST - Low Stress Training - You train the plant to grow more horizontal than vertical by tying it down, gives you numerous cola's if done correctly.

ScrOG - Screen Of Green - Using a net to support and train your plants your goal is to get an even canopy of budsites growing through the screen.

Just a quick explanation, you'll find more detailed descriptions and guides of how to do all of these if you do a search for them

Good luck!