Since the publication of Eye of My Heart, I’ve been running around the country talking to groups of grandparents, and the single most radioactive topic wherever I go is — guess what? — tension between mothers-in-law and daughters-in-law.

I hate it when clichés turn out to contain more truth than rumor, but so many grandparents on the paternal side feel like second-class citizens, compared with maternal grandparents. In many families, the mom’s mom and dad often have easier and more frequent access to the kids. In other families, maternal grandmothers even act the part of what I call alpha nanas. One paternal grandmother who came to my talk in Las Vegas complained that her daughter-in-law’s mother expects the grandkids to be with her side of the family on all major holidays — and her daughter goes along with it.

On the other hand, daughters-in-law don’t necessarily have it any easier. There are mothers-in-law who, while not clinically deaf, routinely ignore their daughters-in-law’s perfectly reasonable requests. “Tomorrow is not a good day to visit,” one daughter-in-law said to her husband’s mother, but the grandmother turned a deaf ear and showed up anyway — and not for the first time.

As a mother-in-law — and one who has worked hard to earn the trust of my daughter-in-law — I’ve come up with 12 rules to help both groups get along. And the key to them all, for both sides?

R-E-S-P-E-C-T.

For mothers-in-law

1. Respect your daughter-in-law’s parenting style — even if you don’t agree with it. Much has changed since you were raising kids. More to the point, you’re the grandparent now and you’re not in charge. Earn your daughter-in-law’s trust by playing by her rules when you’re with the kids.

2. Respect her relationship with her mom — and don’t try to compete. You’ll lose.

3. Respect her relationship with your son — and don’t badmouth her to him. You’ll lose that battle, too.

4. Remember, good parenting is learned on the job — and she’s doing the best she can. Give her the benefit of the doubt, and never forget how sensitive you were as a young parent trying to do your best.

For daughters-in-law

1. Respect your son’s relationship with his mother — whatever your opinion of her. You may get him on your side of your conflict with her, but your entire family, especially your children, will suffer as a result.

2. Remember that all grandparents — unless they are abusive or their behavior is in some way harmful to the kids — deserve to know their grandchildren, and vice-versa. If possible, let all the grandparents spend time alone with the kids. That is the only way they can establish lasting bonds.

3. Cut the grandparents some slack — within reason. They may buy the kids two scoops of ice cream instead of one, or ridiculous, overpriced toys — and then let them stay up an hour past bedtime. They don’t mean to dis you; this is just their way of showing their extravagant love for your children.

4. If you happen to be the mother of sons, beware. Someday, if you’re lucky, you’ll be a mother-in-law with grandchildren, too. Behave accordingly.

For both mothers-in-law and daughters-in-law

1. Boundaries is not a dirty word. In fact, it’s one of the best words in the English language — and in practice, healthy boundaries are what keep us sane and foster friendly relations. Set boundaries for yourself, and respect your in-law’s boundaries. When you do stray into each other’s crosshairs, try to see the situation from her point of view.

2. Let go of your expectations about how things should be and work with the way things are. This means accepting the complete cast of characters who make up your whole crazy extended family, as well as other nonnegotiable circumstances.

3. Always think of the kids. Model the values you want the children to learn. Do you want to train them in sniping and disrespect, or trust and compassion?

4. Remember, the heart is a generous muscle, and there’s enough love to go around. The Beatles said it best: And, in the end, the love you take/is equal to the love you make.

Barbara Graham is the editor of the anthology, Eye of My Heart: 27 Writers Reveal the Hidden Pleasures and Perils of Being a Grandmother (Harper), which tells “the whole crazy, complicated truth about being a grandmother in today’s world.