Never start with less than 16 CON on a melee character
Weapon Finesse gives your to-hit to DEX, if you dump STR you will do ineffectual damage
On a melee char, take Power Attack, but never turn it on. Your loss of to-hit will result in a loss of DPS. Taking Power Attack allows you to take other feats that don't suck.
Play with the UI options. You will need to rapidly change hotbars at some point.
Never use Drow for melee
Never use Elves for melee
Never use Elves
Never multiclass unless you built your char to multiclass.
Never max out any stat scores unless this is a multilife character or you're building a Wizard
Just because INT is not a class ability doesn't mean you shouldn't take a point or two in it. INT determines the number of stat points you get per level.
Your first quest pack should be Devil Assault. Run Chronoscope often, even if it gives no XP.
Always sell the Vials of Pure Water. Never give them to Wash.
Do Wizard before Sorceror.
Always use Drow for Wizard.
If you have the Greater Dragonmark of Finding (human feat only), let your party know. It takes time to buff the chests, and you will never buff it unless they know to wait for you to tell them it's ready.
Marching order is important. Remember, you can walk backwards through your party members, but not enemies.
You can solo Korthos, Harbor, and Marketplace quests. Don't think you can solo level 16 quests.
Never shortman a raid, even if you're all level 19 and you're running low-level raids on normal.
Never solo a raid, even a low-level raid on normal with a level 20 tank.