how to do this?

i went round my freinds and he has got a 3 fot plant.but hes did something to the top so if stopped growing and monster bushed sideways. how would i do that?

I do that with all my plants. It is called topping them. You can keep them about as wide as they are tall. When it starts to stretch, you cut the top off. I found it is best to do it before flowering. If possible, you can cut the tops of the branches and so on. It makes the plant branch out and stay short and stout. I found it not the greatest idea to do to a clone that is mature. I topped mine this year and it was just starting to bud. Now my plant is 13 inches tall with a four inch fatty bud on top. The plant has only been growing for 11 weeks though. By cutting the tops, you make two tops out of the lower branches and so on and so on. Sometimes that is what you have to do if it stretches and you don't want a huge plant.