Despite having played sword'n'board with previous characters, at level 50+ on this one I think I am finally getting the hang of it. In the past I mostly used my shield for bashing and relied on armor (or running away) for protection when the blows were coming on fast and things were getting too dicey.
But I started playing more in 3rd person with my previous character, especially in "open field" melee situations. I've found it helps a lot, and I really resolved with this character to take more time in a fight and pay attention and try to block incoming strikes instead of just standing there slashing away with my own weapon. It is SO satisfying to hear the distinct *clang* of the enemy's weapon hitting my shield instead of me. With previous characters about the only time I ever gained a level in blocking was by paying for training, with this character I'm actually getting "Block Increased to
" messages right in the middle of combat, so I must be doing something right. 
Ah, it's good to see another connoisseur in the fine art of blocking. Have you read
The Mirror?
http://www.uesp.net/wiki/Skyrim:The_Mirror
“Think of melee as a mirror. I look to my opponent's left arm when I am striking with my right. If he is prepared to block my blow, I blow not. Why exert undue force?” Mindothrax cocked an eyebrow, “But when I see his right arm tense, my left arm goes to my shield. You see, it takes twice as much power to send force than it does to deflect it. When your eye can recognize whether your opponent is striking from above, or at angle, or in an uppercut from below, you learn to pivot and place your shield just so to protect yourself. I could block for hours if need be, but it only takes a few minutes, or even seconds, for your opponent, used to battering, to leave a space open for your own strike.”