Well the first part, the pull, is self-explanatory. The second part the sweep, can, at times be a pain. You have to be in heavy(red) stance. They have to be DIRECTLY and I do mean directly behind you, and then hit back and attack. This will execute the infamous one hit kill.
On the subject of countering, there are a few ways to get around it. The first is YOU MUST HAVE ABSORB ON. Most of these spammers are newbs, who when they find out they can't nail you with it, choke. The second is to keep rolling and throwing your saber at them. You CAN throw your saber while rolling. This will keep you out of their reach, and allow you to take them down. That counter works well in duels and ffa games.
Check out ArtifeX's site for a great guide on saber combat in both 1.02 and 1.03. Just click here.