If they occurred at all, I mean.
Were duels more akin to a brawl with swords or were there actual techniques and skills involved?
In my mind I've always imagined them to be kind of like this, if you'll pardon the link to a scene from Monty Python and the Holy Grail.
http://youtu.be/dhRUe-gz690?t=38s
Not flashy, and a lot of kicking and punching.
Here are some images from 14th and 15th century combat manuals. I selected images that hopefully show the sophistication of the techniques being used.
The manuals I pulled from:
There was a similar question asked about a month ago. It might be able to give you some insight. http://www.reddit.com/r/AskHistorians/comments/20x01e/did_soldiers_in_the_sword_and_shield_era_in_big/