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

Unfaithful Cheating Wife Signs - Learn What To Look For

You may not realize it but when you have an unfaithful wife, cheating signs are all around you. You just have to learn to be observant and pick up on things that you may just disregard as being insignificant. Quite often the husband is the last to know when his wife is having an extramarital affair. You may notice that some of your friends are uncomfortable when in he presence of your wife or seem to be more guarded in their conversations. This could be they already know what is going on and do not want to be the one to break the news to you.
Often a cheating wife starts to display behavior that just doesn’t seem to make sense. This can include such things as taking up activities, which she previously condemned or had no interest in or finding excuses to go out every night, leaving you home alone. It may start with her picking fights with you over little things and then using that as an excuse to get out of the house for a while. It is normal for all couples to have disagreements when one or the other might need a change of scene to cool down, but this happens on a regular basis, you can be sure there is something else happening.

Even though you buy your wife gifts, does she seem to have more gifts than usual and not from you? This is a warning sign that there is someone else in her life, even if she says that she bought them herself or just picked them up because they were on sale. This is really something that should send up a red flag if she starts to wear a new piece of jewelry over one you gave here and that she claimed was her favorite.

A wife that seems to be distant and keeping secrets when once she used to share everything with could be cheating on your. Simple little things you do make her angry very easily and she doesn’t seem to be comfortable when you are around. Other indications that your wife is being unfaithful include many hours of overtime that doesn’t translate into pay at the end of the week. She may be claiming that she has all this overtime, but when there is no extra pay attached, then it is time for you to find out exactly what she is doing during those hours.

Another sign that your wife is cheating on you can happen when one of her coworkers asks how she is feeling seeing she was home from work and not feeling well. However, both of you left the house at the same time that morning and when you called home there was no answer. You should discretely ask if she had to go home sick or if she didn’t come in at all. You can confront her with this to find out what explanation she gives for taking the day off. It will arouse your suspicions and you may take some time off yourself just to check up on her.