Thin lines.
The closer the distance to the wall, the thinner the line. To bring the can very close to the wall you need to tilt it.
Also, use an outline cap for thin lines. A fat cap will put so much paint on the wall that most of it will drip down. (Does not look cool.)
To get even thinner lines, additionally hold your can such that the upper side points towards the direction you are painting. I.e. hold the can vertically for drawing vertical lines, horizontally for drawing horizontal lines. You can get very sharp lines like that.
Obviously, spraying too long on the same place will leave drips as well. Very thin lines need to be painted quickly.