text: I used to sing professionally in a Top 40 band in the 80's. I wonder if you are speaking about in a performance setting. In that case, you always start with a fast, driving song to get the energy in the room up. As far as band sets go, this is the usual fare: 6 - 8 songs per 40 minute set (20 minute breaks in between) and a distribution of something like 2 slow, 4 -5 fast OR 1 slow, 4 - 6 fast depending on the songs used per set.  If you are doing a one number performance go for something very driving and energetic and meaty ........if you are doing 2 numbers start with the fast and end with a slow song. If doing 3 songs, do fast, slow, fast.  And save the very best for last. Whatever you do, make each song one that brings the house down and has the audience 'over the moon' with your performance.