Do not let him sit too long over the book, encourage him to be focused, limit the time for each subject, if necessary. If your child doesn’t understand something, ask him to read you that part of the book, and then say how he understood it. Ask him questions, and let him arrive to conclusions on his own. You should never read and present the complete solution.

I used to help out with my nephew up until he moved away a few years ago. Sometimes he'd sit in the garden table so he can work in daylight, but most times I'd have him study in the room. I would normally have him read over his lessons and answer the homework himself but I'd step in whenever he couldn't answer the questions. Like znljubica, I'd also ask him to tell me what he thought of the lessons just so I can see what he'd learned.

Whenever exam time came, make him some mock exams that he could answer.

I guess I could share that I also work for a tutoring company, and I'd suggest that if you're too busy. However, even if you're planning on hiring a tutor for your kids, it's still a good idea to spend a little time with drills and discussions. It's still a great way to bond.

I agree, tutor must not represent opposing methods and attitudes of yours. You are the parent, you are responsible for your child, you lovest your child!
If the tutor has objections to your methods, attitudes and behavior , he needs to talk to you, not to the child. Therefore, please be in touch with the tutor and synchronize your relationship with your child.