Years ago, when I first started leading worship, I typically went into each weekend rather unprepared.  I guess my thinking was that flying by the seat of your pants was somehow more spiritual than planning a set list.  I had the misunderstanding that flow in a worship set means no structure.  I have come to learn that my thinking was way off.  I have found that the better prepared and rehearsed we are, the more freedom we have to be creative.  When we feel ready and confident, we simply play better.  Think about it, what is more spiritual, having no set list and waiting until the last minute to hear from God or taking the time to pray ahead of time and hear from God.  God can and will give you wisdom in advance of the weekend service.  My day for putting together a set list is Wednesday.  That gives me the time to think through background graphics, send the set list to the musicians scheduled and make sure they have the sheets in advance of rehearsal.  You also can check with the lead Pastor or whoever is speaking that week to see what songs will help reinforce the message.  The bottom line is that good flow in a worship service doesn’t just happen.  Good flow is a product of being well prepared and well rehearsed.