How do you prefer the client from thinking your going to work 8 hours a day, 40 a week, etc? Or even worse, expect they get you for more time in the day or week

How do you prefer the client from thinking your going to work 8 hours a day, 40 a week, etc? Or even worse, expect they get you for more time in the day or week? "I'm paying you x got today, here's 12 hours of work..." Or think they are v trading dollars for your labor and if you finish early on a day, go take out the trash and clean the bathroom. Obviously you define what work will be performed. Just wondering and looking for what language people use to address these issues. Thanks.