Forget lipstick on the collar and late nights at the office. By the time your husband starts displaying this classic suspicious behaviour, it's likely too late to stop him from straying. Instead, Elizabeth Landers, co-author of The Script: The 100% Absolutely Predictable Things Men Do When They Cheat, says to watch out for the warning signs that come even earlier.

Landers says she and Vicky Mainzer decided to write The Script after hearing similar tales from betrayed wives across the United States. "We kept hearing the same story over and over again," she says. "As we started doing research and interviewing hundreds of women, the same words and phrases, these lesser-known warning signs kept reappearing, no matter the age, the background or the part of the country."

Not all men cheat, says Landers, but those who do follow the same rules. "Once you know the script, you can interrupt it and you can protect yourself if your husband has cheated." Landers shared with us five of the most predictable things men do when they're thinking about cheating.

1. He starts criticizing everything you do. "He's trying to make you doubt yourself, become defensive," says Landers. "You'll come across as argumentative, difficult." Often, she says, he'll suddenly pick apart something you do well. If you're a renowned party-thrower, he'll tell you your canapés were overcooked and your guests were bored. The point is to throw you off balance.

2. He starts offering "suggestions" to improve yourself. Again, says Landers, this is about making you appear difficult. "He'll say, ‘I keep telling you to lose weight or get a job or go back to school,'" she says. "As though you are the one with the problem, a problem he has been trying to fix."

3. He calls you crazy or depressed. "When he starts acting suspiciously later, staying out late, you'll question your own suspicions," says Landers. "After all, he told you that you're crazy -- you'll start to wonder if you are."

4. He starts doing strange things with money. Money or bank statements are suddenly missing, he's carrying around lots of cash or he's spending too little cash. "He could be trying to get money together for when he eventually leaves," says Landers. "Or he could be trying to cover his tracks, or not spending money because he's staying in with his mistress to avoid being seen." Any behaviour related to money that is out of the ordinary can be considered a warning sign.

5. He buys you big, expensive gifts. "You'll think, how could he cheat on me when he bought me this big diamond?" says Landers. "But it's more likely he bought the gift to throw you off or to hide his own guilt."

Knowing the telltale behaviour is a way to arm yourself against betrayal, says Landers. "When he starts acting out parts of the script, you need to take action," she says. "If you think something is wrong, it probably is. Don't make excuses and take action. A doctor would say to treat the pain early before it gets really bad. Our natural instinct is to let it go, not make trouble, but you need to do something."

Landers suggests getting counselling together or, if he refuses, go alone. Find a resource or facility that can help you, whether it be a psychiatrist, a support group or your church. If you don't have help available, Landers advises keeping a journal and writing down any suspicious occurrence. "It will help you assess the situation," she says. "You can interrupt the script by not going along with it. Don't allow him to convince you to doubt yourself."