1. Take them to lunch and ask the question "what do you feel is the weakest part of the practices/performances from a technical aspect?"
2. Meet with them after the service and talk about what went right/wrong and brainstorm ideas to fix the problem areas.
3. Ask the worship leader for a list of the songs a few days ahead of the service so you can hear the mix they are trying to match. If they say, we are doing really slow/fast version of the song with different instrumentation, then talk with them about which instrument will be leading, which instruments will be used, in short, what is their plan for the song.
4. Pat them on the back after a service and say "great job this morning."
5. If they play a guitar, ask them how they started playing it. The point is to build a relationship.
6. Show up when the worship team practices. Some churches require this and some do not. You can gain insight into how the band interacts, offer suggestions if warranted, and be open for feedback. You can also experiment with effects, eq, and mixing.
7. Build a relationship with one of the band members. In doing so, you now have one more person in your corner.
8. Build a relationship with all of the band members. The more you are seen as part of the team, the more your input will be respected.
9. Start dating their daughter…if you are male and single :)
10. Invite them to come in early and help you set up the stage. You might even bring them into the sound booth for a whole service on a day when they are not leading worship. You are showing them the different aspects of your job as the sound tech. Much of this they may never have even considered.