Trying to make it short.
- You are CC/support class. Do not focus on doing plain damage in groups.
- Learn difference between stun and daze. Use skills that stun effectively to keep mobs immobilized as long as you can.
- When you get it, realize the importance of SOP:righteousness, SI skill. Keep tank warm and walking so he can take on those mobs that would otherwise kill you. Specially low level tanks need usually all help possible since they are just learning.
- Debuff. You get nice skills already in early levels.
- flanks was already mentioned, but as important is also harried-debuff, get it with pet hitting on enemies back. It will slow them down to make your kiting more efficent.