Welcome to Pery's Guide to the Clockworks!
Shields are important in Spiral Knights, and you know that! Players know about some of it's abilities, but you can use these abilities to their full potential!

Shield Bashing (Left Shift+ATTACK):
Most players know the shield bash, but they don't use it most of the time because we think it it useless and it puts us in danger. But to properly use the shield bash, you use it on a monster while pushing it away from a group. Then, you either use a sword combo to interrupt the target monster's attacks OR back away from the monster and use your gun or bomb. NOTE: It's easier to perform this ability if you hold Left Shift first.)

Shield Charging (Hold BLOCK, then hold ATTACK and release BLOCK):
Many players don't use this ability, but it is extremely useful with some swords and guns, because you can charge your weapon without attacking. Weapons that it's useful with are slow swords, autoguns, and magnuses.

Shield Bumping (Press BLOCK while near a monster.)
To use this to it's full potential, you have to bump away both monsters and their attacks. Keep your shield lowered, and then raise your shield between the monster's dash and attack to bump the monster away. Your shield will either take very little damage or no damage at all. It's good against most attacks but the most important attacks it protect you from are zombie's lunges and jelly cube's tackles. This is, in my opinion, the most helpful shield technique in the game.

That's all for this post. I hope this helps! If you have any questions, comments, or suggestions, please reply!
The shieldbearer guide on the wiki can be found here: http://wiki.spiralknights.com/Shieldbearer_Guide

-Pery :p

TL,DR(Too lazy, didn't read.): Oh, come on, it's not THAT long; go back and read it!