Lemme fix this...
In general, I have found that you have to be very particular on how you carry out attacks.
If I attack while moving forward swinging RtL to strike with the strong of my blade, it will hit at the left thigh. If I give myself a longer start up on my swing, It gives it more time to rise to hit the upperbody and head. LtR swings can seem to start high and stay high compared to RtL attacks. If you're trying to get them in the head, try for a really, really long swing to hit them.
If you can dodge their attack or parry them for the counter-attack, you can get a nice, long strike to the head for massive damage. It's a good power hit that can win duels.
Holding an attack is possible, you need to back-swing, and hold it there. It's not as easy as some other games, but with enough practice, it can be kept on queue. It doesn't appear to be much use against the AI as it's not possible to trick them like so.
A simple strategy would be to swing RtL if they swing LtR, or vice-versa. It lets my attack get right past and get them in the flank.
The only time it's better to change strategy would be when your opponent is using a polearm. When they backswing, attack immediately to catch them with your faster attack.