1h is one of the hardest weapons to be effective with in that you really have to refine the raw speed bonus with properly landed hits in the correct timing of the animation. When I attempt to connect a hit, I visualize a hard hit(or a series of unpredictable feints) that is also visually appealing. If you just swing without further thought, you will become predictable and quickly spammed. A good duelist/player will spot someone who doesn't use his wits to fight in a few seconds and spam them.
tl;dr Think before you swing.
Some pointers for improving on the long run:
-Be ready to block a lot(if shieldless)
-Try chambering, it will get you a long way when mastered
-Practice feints
-Learn the ranges of your weapon
-Focus on your opponent as a whole, not only his attack directions, that includes vs multiple enemies
-Pretty much same as above; don't tunnel vision
-Spent at least 1 hour per day on duel server(preferably longer)
-Always duel someone better than you
There is more, but I might make a really conclusive tutorial with videos sometime next year or December(next year).
