Manginae's numbers are spot on - shoot for 8% hit and at least 26 expertise.
I think vigilance can be a tank's best friend in regards to aggro, and I have it glyphed, as well. The glove enchant for parry/+2% threat is also mandatory. I would also glyph for devastate and make Shield Slam/Devastate your main attacks. Obviously use Thunder Clap and Shockwave on every cd, as they are they easiest way to target the whole mob. But I believe glyphing for Devastate and then tabbing through the mob while using Shockwave, Thunderclap, Revenge and Shield Slam on every cd is the best way to hold aggro.
Always stay behind your tank and in front of your healer.