Make an evaluation sheet, with No. 1--absolutely sure I do not understand the passage, No. 2--sure that I do not understand, No. 3--sure that I understand, and No. 4--absolutely sure that I understand.
Select a passage in a book that your child has not read before.
Ask your child to read the passage. Or read it to your child.
Ask your child to indicate his/her understanding of the passage in the book. Ask your child to rate his understanding on the evalution sheet.
Discuss the passage with your child. Ask a couple of questions about the passage in the book to check your child's understanding.
Ask your child if she wants to change the rating. Check how well your child's evaluation and her understanding of the text corresponds. Stickers can be used to reward the evaluation of the understanding.