Cheating individuals may loose attention in the activities in the home or day to day life functions. They don't show interest in the livelihood of you or the children that live in the home. Nor do they have and desires to do any fix-ups to the home, lawn care, house repairs, etc.
Mutual friends may begin to act strangely towards you; they either know of the cheating or have been given stories about how horrible of a spouse or significant other you are.
The cheater may have a definite change in attitude towards everyone in the home, especially the mate, (if he/she didn't act the way they do, well then maybe I wouldn't be doing the things I do).
Cheaters may stop confiding or seeking advice from you, spend more time away working, shopping, with friends, joining a fitness gym, etc.
Cheating may show in cell phone, computer use or even with extra mileage on vehicle regularly used. A cell phone may be kept always at hand or in purse, maybe set on vibrate and calls or text ignored around you. Computer use while away or in bed late at night and the cheater may be meeting further away in vehicle.
Grooming habits will change. Cheaters will be more attentive to their person, (the way they dress, frequent bathing, physical fitness, grooming of their hair, switching of colognes, etc.).
Finances. "If someone wants to play they have to pay", therefore keeping an eye on their monies, (check stubs, bank account balances, credit card bills, etc.) would tell you whether their spending more money than usual.
Intuition (gut feeling) that something is not right usually is a sign you may have a cheating problem, "When in doubt Call us and Check them Out".
The answer is it depends on your particular investigations; location is a huge factor when it comes to surveillance.
If you suspect your spouse of cheating, you need to find out for sure. You can't afford to be the last to know. There are many practical reasons why you need to search for signs of infidelity if you think your spouse might be having an extramarital affair.
If my ex husband is not living up to his alimony and child support obligation and I know he works part time for cash what should I do?