Here are a few of mine:
1. Do not neglect to pick up the prestige powers from the P2W Vendor at level 1. They will help you a lot longer than they will the DPS classes. The Nemesis staff, in particular, does damage plus knock back. That can save your butt when solo.
2. DFB and DiB are popular for a reason. They provide quick experience. If you already know how to play your archetypes, then joining them at the low levels can help push you to where your powers make a difference.
3. If it's a slow night, don't be afraid of joining a farm team. It's boring and you won't learn anything (except perhaps gossip) but it will help youmove through the leveling doldrums.
4. I learned this back in the day playing a cleric in Everquest. Find a group of villains that are especially vulnerable to your powers. I like playing Dark/Dark. Anything psychic pretty much has my name on it.
Hope these help!
What are some more?