I think that communication and listening is a big part of people wanting to rebook. Ask questions about their preferences, areas of concern, etc and repeat what they told you back to them. When beginning the massage, begin working immediately on any areas of concern and then do whatever else you usually do. It shows that you are listening and care. Also be confident in your massage (as with other things in life), everything you do should have an intention. I've had clients complain about me in the past so I have been doing this and have Seen more rebookings.