From your build, I would think that you would be trying to get a lot of kills. That, sadly, is not what being a shielder is about. A shielder is a support unit, and is best used in formations that protect non-shielders from arrows. However, you can still maintain a positive kill/death with a shielder, I usually do that quite a bit. With this in mind, if you still want to be a shielder, I would recommend this:
Strength: 21
Agility: 15
(There are a few conversions from skills to attributes, whenever I have 2 extra points floating around)
One Handed: 139
Polearm: 58
Ironflesh: 7
Powerstrike: 7
Shield: 5
Athletics: 5
Weapon Master: 5
The 7 powerstrike and ironflesh make this build take quite a few hits and deal considerable amounts of damage. Proficiency is enough to swing fast enough to avoid spammers, and if you want to put it all in 1h, go ahead.
Now for equipment. I would recommend something tough, but not heavy. Plate is too heavy for this, I find that the tunic over mail provides decent protection and freedom of movement. For kills, I recommend the military cleaver. If a tin can comes your way, it has a pierce damage secondary which can deal with them. If you want a versitile weapon, the knightly arming sword is what you want. For a shield, if you want to remain light, pick something smaller than a board shield. The Knightly Heater shield works fine. However, a board shield will last longer. If you plan on not carrying a polearm (which I recommend, it comes in handy against cav), you might as well carry the heaviest shield you can get! A war spear is pretty good to take for a polearm.
As for playstyle, people enjoy readying their strikes and waiting for you to put down your guard. Don't fall for it. Most will get impatient and hit your shield.
If you find yourself in a duel where you're not in danger of getting hit from behind, try to get around to the side of your opponent.
Keep a look out! When in an open area (bad idea) and approaching the enemy, take out your spear and look around with the ` key. Simply having a spear out can scare away some cav, but when I wasn't looking, I've been killed, even with a spear.
There, I'm done writing on this, feel free to use the build above, I was thinking of trying something new anyway.