Ideally, my own preparation involves prayer and an "examination of conscience". There are different ways of doing that. A number of them can be found online: this
is one example, but there are others which pop up fairly easily. Typically, I will use one of these if I'm pressed for time, but if I have time, I'll read Exodus 20 (the Ten Commandments) and Matthew 5-7 (the entire Sermon on the Mount), and perhaps other passages if I feel so moved, and I'll ask myself how I live up to those standards. I try to keep everything in my mind, but I might jot down some notes if I feel I might leave out something due to nerves or the sheer number of my sins. I pray the "Seven Penitential Psalms", the Prayer of Manasseh, my own prayer, and try to relax.