The best way to improve your DPS is to attack more. I'm not talking about stacking haste so that your attacks are swift as lightning, but rather about not missing any opportunities. In order for a rogue to deal maximum damage, he needs to be in melee range of something that needs to die at all times.
Staying in melee range can be difficult, as bosses are always tossing out pools of fire and knocking us back into the walls. Rogues need to be tenacious; we need to be vicious dogs that won't let go of our prey for any reason. We need to hustle between targets, minimizing the amount of time we see "Out of Range" at the top of our screen. In order to ensure that we're on our targets at all times, we need to learn about how melee mechanics work.