I always discuss expectations and requirements at the M&G. Some clients require that the sitter stay overnight, some don't. I usually just move into the client home and use it as my base of operations, following my own routine but at their house not mine. I will come and go, with client permission, to do other dog visits, check on my house a few times, attend church, etc. but not be gone more than 2-3 hours max.
I have read of a few clients who require 24/7 care and presence in the home. That should be charged at a premium rate because it prohibits you from your normal activities and visiting other dogs.
As far as tips: at the M&G get the alarm code and password, and have the owner demonstrate it to you. Test the key to make sure it works. Ask about the following: where will you sleep, what use of the kitchen are you allowed, how appliances, TV work, what to do with linens before you leave, how to return key if necessary, what day is trash picked up and location of outside trash containers, any automatic lights, Wifi network name and password, time of arrival and departure, will anyone else have access to the house and be coming in (housecleaner, lawn, etc). As well as the usual dog-related questions.
After you arrive, just relax and enjoy. I bring books, my cross stitch projects, and my laptop. Your main responsibility is caring for the animal(s). I try to leave the house as clean as it was when I arrived, if not better.