Beginner / early level tips:
* Make sure your gear is up to date.
* Lead a pull with shield lob, followed by at least 1-2 flashes.
* FoF increase emnity gains from your attacks as well as flash.
Dealing w/ High DPS party members in low level content on a low level char:
* leading with shield lob is very important. Its an inital threat boost but also some players see this as a signal to attack target X. At the very least, it creates a situation where particularly aggressive party members can only attack 1 target safely and helps create scenarios where they both attack the same target.
* FoF is important! On bosses, make sure you use it as often as possible. On trash, lining it up with say, your Bard's raging strikes will help ensure you keep threat.
* Don't forget about the other mobs in the pull. You only need enough threat to hold a target til it dies. If you've met that requirement start building a threat lead on the other mobs. Also remember that periodic use of flash will help build a threat lead