I love SCROG.
My first grow was in soil. Four plants in a 28" x 38" x 48" DIY tent in fabric pots. I harvested just under 1 pound.
My second grow was hydro. Same tent, same lights, but only three plants. I netted just over 1 pound.
SCROG is an easy way to completely fill any tent with colas with relatively few plants. As was mentioned above, you can do it with a single plant if you want, but having two or more gives you some room for error.
My method is pretty simple. Let the babies grow until they have 3 or 4 nodes, then FIM them. You can Google that training method, but its basically just pinching off the very tip top part of the plant. That forces it to grow two new branches from that point. I then FIM the new branches at least one more time and usually two more times. I end up with around 15 to 20 branches on each plant.
Once the plants get to about 10" or so above the soil, I add the SCROG screen just above the canopy. Now you just bend all those new stems over so they grow sideways UNDER the screen. They will immediately want to turn and start growing UP again, so you will be working on this all through the veg stage - constantly pulling them back under so they grow more sideways. You will want some twist tie type material to hold stems in place at times. Sometimes, you cant bend them under without breaking them, so you may have to tie them down above the screen.
As they grow sideways, they will start to produce new stems that grow out of each node. I also keep those stems growing under the screen. They in turn will also send out new stems. So this is a pyramid scheme of growth as far as new stems. One main stem gets FIM’ed and makes two new ones. Those get FIM’ed and now you have 4, then 8, etc etc. Then each one of those can put out several new side stems as they grwo sideways. Its awesome 
You keep that up until the screen is 70% to 80% full - which wont take long. At that point, I switch to 12/12 timing on the lights and start the flowering cycle. The plants will continue to grow and stretch for the first couple of weeks or more of flower. If you have timed is right, you will finish filling the screen up just as the stretch ends.
You should end up with a bunch of colas, all of similar heights, that totally fill your growing space.
