LST stands for Low Stress Training. It is a method in which the branches of the plant are tied (or twist tied) into more lateral postions. Instead of allowing them to grow up like a tree, you train the branchs to grow outward like a bush. This allows more light to get to the bottom budsites thus increasing yeilds. This training is done gradually over time, hence the low stress part.
I have tried it with the twist ties and it does work. I think this is better because you can adjust the branch a little at a time. Just wrap a plastic coated twist tie gently around the branch two or three times and then gently bend it out a little each day. Make sure not to break the outter "bark" of the branch.
i did training on one of my old grows by puting a pipecleaner around the stem of the main stalk in a loose spiral with a rubber band tied to it and then ran string from the rubber band to a point about a foot or so away from the bottom of the pot and put tension on the string to pull the top sideways and shortened the string over a week or two till the top of the plant was almost sideways and about the width of my hand above the top of the flowerpot this made all the side branches grow like multiple tops and really increased the size of the end buds on those branches