It's widely accepted among players that the optimal times to play slots are early morning or evening, with peak hours typically occurring between 8 pm and 2 am. Take some time to watch the particular machine to gauge when it is most likely to pay out.
Tuesday should be slow, depending on what is happening in town that week. As a general rule Sunday is the day more people check in/out, followed by Friday. Seems like Monday/Tuesday is the slowest and Friday/Saturday the busiest. It really depends on what is going on.