First off, do what you can with out magic. The closer you are to where you are trying to go, the less juice it takes to get there. Shadow is far different than total darkness, so wear dark greens, Grays, or blues, not actual black clothing.
Second, tailor it to what you are hiding from. Humans are tuned to notice movement, bright colors angles that point up (the shape formed by the joint of your arm and torso) not down (the shape formed by tree branches). We notice high pitched noises and the sounds of sneaking (a door opening slowly) do be quiet, but don't sound sneaky. If you must make noise, just get it over with.
When it comes to the magic portion, obviously, believe you don't exist, or at least that you cannot get spotted. Don't get nervous. Try to project the same energy as your surroundings. My method is to listen to the back ground noise and hum in harmony under my breath.