Most tech volunteers have detail type personalities with a fair measure of musician's ego mixed in. They have a genuine desire to do the job right and invest quite a bit of time in making sure things go smoothly. Unfortunately, the only recognition most church sound engineers get is when things go wrong, like a problem with a mic not being on when it should be. Don't embarrass them publicly. Be sure you encourage them privately and honor their efforts from the pulpit on a regular basis.
Nothing hurts an organization more than a lack of communication.
Go out of your way to communicate any changes with this weekend's service to your sound team. Include them in your planning sessions for all services and special events as early as possible. Details that you may take for granted, or think unimportant, may be the very pieces of information your sound team needs to do their job right. Your musicians and singers probably rehearse the material for worship sets quite a bit. If you refuse to schedule soundchecks and rehearsals, then don't complain to your sound team about the poor job they are doing with the sound.