I would say that the most important thing to focus on, #1, is making sure each note SOUNDS clear and strong. As guitarists, we focus so much on the physical and technical aspects for everything but the way to approach EVERYTHING is to let your ear decide. That being said, technique is important to achieve those good sounds. I would say the thing to focus on the most is for your fingers to come straight down on top of the string with the harder tip of your fingers, no at an angle with the soft parts. This differs a bit once you get into string bending and vibrato.