1. Call your husband every half hour to make sure he's not with a woman.
2. Wear sweatsuits, housecoats, and the most unsexual clothing you have so that your husband knows you've only got eyes for him. If you can, try to gain weight so that other gentlemen don't hit on you and threaten your marriage. (*Don't get too fat, don't be stupid about it)
3. Join a book club. If you're reading a good book, your mind will be off cock and away from affair territory. Plus you can talk to your husband about the characters and evoke conversation.
4. Have a date night once a week. Go out for dinner and a movie and get one of your leggy 15-year old babysitters to watch the kids. Let your husband choose the babysitter. And the movie.
5. Fake orgasm with your husband as much as you can. If he feels he's satisfying you, it's less likely he'll feel the need to satisfy another human being.
6. Give birth to a baby. It bonds you forever and often saves marriages when nothing else works.
7. On anniversaries or special occasions, present your husband with stripper coupons or vouchers for the massage parlor down the street. Prostitute sex is not an affair, it's therapy just like the spa. If you're uncomfortable giving him this, then turn a blind eye while he does it anyway. He'll think you're really cool if you do it though. Again, prostitute sex is not an affair.
8. Divorce your husband. Not being married is the best way to affair-proof your marriage.