My top pick for tips on how to catch cheating is this book by Sarah Paul

How To Get Over The Affair - Dealing With A Cheating Wife

Dealing with a cheating wife is one of the hardest moments in a marriage for a loving husband. It usually starts out with just a feeling that your wife is having an affair. You don’t have any definite to go on, but you have noticed changes that you just can’t ignore. So you set out trying to find out what is going on. No matter how secretive she might be, there will be signs that will alert you to an affair. Even though you know that you may not like the results of your investigation, you do need to know for sure so that you know what you are dealing with.

The signs are basically all the same once you know what to look for. There will not be any one sign, but rather a combination of signs. These can include any or all of the following:

* Working later hours, but not receiving extra pay
* She has new friends and you don’t know any of them
* She makes excuses for not attending family functions
* She changes her perfume
* She stops wearing her wedding ring
* She comes home with a scent of aftershave on her that isn’t yours
* She has less desire for lovemaking
* She doesn’t want to hug or kiss or hold hands
* She makes up excuses for being out of the home
* She shuts down the computer screen so you won’t know who she is talking to
* She makes sure she erases the caller’s list
* She is more secretive when talking on her cell phone

Although by itself it is not a sign that she is cheating, but when you notice other signs and then you see she is paying more attention to her appearance, perhaps by going on a diet or joining a gym, you should be on the alert. If you can devise a way to get hold of her sell phone, you can check to see whom she has been calling or who has been calling her. Then using a reverse telephone look up, you can find the name and address, so you have a name to start with. Then you can listen attentively to see if she does bring up this name in any of her conversations with you.

You may have to revert to following her discreetly to check up on her activities, just to see if she actually goes where she says she is going. You can even start a casual conversation with one of her close friends to see if they are uncomfortable talking about her activities and don’t want to be the one to let you know she is cheating on you. Best friends usually know something is going on.

When you do confront her and she admits the affair, at least you will be prepared for it. It is harder to deal with the situation if you find out and are not aware of anything going on.