DONT TAKE CLONES !! RE-VEG the plant.. It takes the same ammount of time as a clone, but bigger, Unless your plant is in the ground.
harvest all of the top buds and leave some lower growth and re-veg,
But if you can't move the plant take a bunch of clones from the lower branches like everyone else has said.
the smaller the clones the less chance of them throwing roots if the plants are in flower.
So take atleast 6 inch clones if you can, for best chance of it rooting.
Peace and Happy Growing