When tanking each time you target a mob you'll see bars on the left side of the screen showing your current hate and everyone else's current hate against that target mob. Start off with a Fast Blade into the secondary Attack which generates incredibly high threat! Use this on all the targets you can, while tossing out a Flash here and there. Dont be shy to blow your DPS CDs at this point as well as Blood Bath from the MAR (level 8 i believe, worth it! Its awesome for tanking, heals you and generates extra threat because of said healing)

Swap targets while remaining locked onto your current target. If you have to mark your current target with a marker so dps know to focus on that one. Hope that helps!