1. Don't let family ties be an excuse for rudeness.
For most interactions with your adult child, you must be diplomatic. The guideline here is to act as you would behave if the person were not related to you. Imagine that you are dealing with a younger adult with whom you are close, but who is not a part of your family. It may help you to have a particular person in mind--Johnny, for example. When you are considering saying something to your adult child, ask yourself, "Would I speak this way to Johnny?" If the answer is no, then don't say it, or say it in a different way. Our family members deserve at least the same courtesy that we extend to the world at large.
2. Think before you talk.
That is, of course, a good rule for almost every person in almost every situation, but it is also difficult for us all. Everyone at some time or another is going to say something he or she should not have said. Forgiveness is more likely, however, if we have built up a history of being kind and non-interfering.
3. Build a foundation of good feelings.
Praise your child's parenting skills whenever it is possible and appropriate. Simple statements such as, "I love how you explain things to Thomas," can be powerful in fostering the feeling that you approve of your child as a parent. And parental approval is probably still important to your adult child.
4. Don't make statements about how you raised your children.
Such statements often have a built-in critical tone. You are allowed, however, to tell funny stories about how something you did as a parent backfired on you or to relate in a kind of "gee-whiz" manner some of the strange things parents used to do--"Can you believe I bought you a cap gun when you were three?" Otherwise, be aware that child-rearing philosophies and practices have changed since you were a young parent. Respect that. You don't expect your children to drive 30-year-old cars; don't expect them to follow 30-year-old practices. Once my daughter was having a tantrum, and my mother-in-law advised me to pour a glass of ice water on her. I resisted her suggestion, of course, just as my children might reject some of my suggestions.
5. Remember that this, too, will pass.
Children outgrow the terrible two's and the whiny three's. Adolescents will eventually realize that adults have some knowledge about life. Be patient and don't confuse normal developmental tendencies with serious problems.
6. Love your adult child as well as your grandchild.
Children sometimes humorously complain that once they provide us with grandchildren, they never get any attention. Make it a point to relate to your child as an adult and discuss jobs, movies, politics and topics unrelated to your grandchildren. Do things with your children that don't involve the grandchildren. Appreciate them as adults.
7. Have faith that your child will do a good job.
After all, he or she had a great teacher!