Listen to the sound of your strings before even using them!
Described from Marin Mersenne in Harmonie Universelle (1636), this test is used by string-makers to check if the string is even or false, by watching if the fuse of the string is regular or not.
But there's something more for a sensible musician: try to do it with your eyes closed. Don't you start to feel in your hands the vibrations of the string? it's like when you touch the soundbox of your cello while playing, you feel the vibrations. Same thing here.
If you concentrate you can guess the quality of the sound. You can feel if the vibrations come to you evenly, smoothly, or if they are rough, not regular. Then open your eyes and check if what you felt is confirmed by the fuse you see.
If you exercise a bit you'll know the sound of your strings even before installing them, which could be a pretty good advantage!