What is the best way to remove duct tape residue?

I have a window on my car that doesn’t work. I’ve been using duct tape to keep it from falling down but this seems to no longer work as well as it used to. I’m thinking its because of the tape residue left over after every time I replace it. Dust and leaves have gotten themselves stuck up on it and are causing a lack of stick-to-it-ivness and with winter coming, that won’t be friendly.