At the risk of making some secret keepers mad, here's some of what I know from experience and learning from others:
Null - tripping the enemy, backslash, look up to launch. Make it stronger by doing it with your back to the enemy. Make an epic launch by facing down and facing he enemy, then spining around and looking up while you backslash.
CenterBlock - face center of map and block. invulerable to melee attacks while doing so, regardless of where they hit you.
Reduce chance of being nulled while dash attacking - look down while doing it, hit enemy from side rather than front
CenterDash - face center of map and dash attack. You are now hard to null.
You can interrupt a long dash attack with a roll, especially with Obi/Ani (a must with them, to avoid the long recovery).
How to null Vader: when he dashes at you, dash at him and quickly launch your dash attack at him before he launches his. Works really well with Obi/Ani.
Certain characters have a strong forward attack that can be used to null without backslashing. The ones I've found are: Emp and Dooku.
Whirlpool - my invention (I guess), with Obi/Ani, do the dash atack thru the enemy and spin around so your saber keeps spinning into them from front to back.
Saber streak - a visual glitch, double tap saber throw, quickly switch to your other force power, and tap it. Your saber will make a solid streak of light (careful, might frame lag you a bit).
A lot more to know, but these are a good selection of the basics.
Most of this is just for no force dueling, but it can be handy in a force battle where you have been force pushed into a wall and have a split second to launch one attack on the enemy who is dash attacking you. The proper response is to backslash.