How to Catch Your Spouse Cheating

There are a few items that can help you tremendously. Audio devices can be very effective.
Remember this point. If your significant other is having an affair they will call their lover the first second the coast is clear and very rarely will go more than 12 hours without contacting the other person in some form.
With that said buy a pair of digital audio recorders. They are fairly cheap $30-$60 and often can be set to voice activate. So if your spouse "goes to the store" for no good reason, make sure the audio device is in the car. Bingo, can guarantee that if they are cheating you will be able to hear the proof in the form of a eager phone call by the offender. You can also use these devices in your home when you go to work. Many of them will record for 9-10 hours so you should be able to get most of the days activities on tape.
Another possibility, and one that I personally used that was really great, is a GPS enabled cell phone. Not for directions but one that has the kid tracker feature enabled. You can probably get the phone for free or for the price of activation and then subscribe to the tracking service for $20 a month. Since you will not be using any minutes on the phone it will most likely not cost you anything else. You can then hide the phone in your spouse's car and wallah, you can now see exactly where they are as long as they stay in the coverage area. Particularly useful when they say they are going to work but instead they are no wheres near it. You get the idea. This is really a sure fire way to catch them in the act.

Another useful tool is a key logger. If your spouse uses the computer, its possible that he or she might be sending sms messages (txt messages), emails, or possibly looking at lawyers, places to live, etc. The key logger will run hidden on the PC but log internet traffic, keystrokes, emails sent, Instant messaging software and then holds them in a log file for you to look at when the coast is clear. The one I used even sent reports to my email along with periodic screen shots of activity. Pretty awesome. Here is the one I used Win Spy - Detect a cheating Spouse
The results are definitely worth it.

You have probably heard several of them before. Here is a list of signs that may indicate your partner is involved in an affair.
1. Changes in appearance. Your spouse is suddenly joining the gym, or working out more often than normal, sometimes a diet is involved. New haircut, coloring hair, shaving at all or more often. Guys tend to clean up tremendously when they are in a new relationship.
2. Changes in activities at home. Your spouse may make frequent and sometimes pointless trips to the store or to run other errands. They may say that they are going out with friends that to your knowledge they haven't spoken to in months or years. (When coming up with lies to protect an affair, the offenders do not usually use close friends or friends that may come in contact with you, in case something slips) Your partner may be seen stepping out to use their mobile phone, sending text messages while in another room, etc. If you walk in on your spouse and they close their phone suddenly or appear to be hiding the fact that they are using it, this is a big sign that they are up to something no good.
3. history of calls and txt messages are almost always deleted on their phone. Reluctance to let you see the phone bill or put any receipts into the check book or accounting software.
4. A change in affection towards you or possibly your family. Guilt can sometimes drive a person to be over affectionate towards the ones they are hurting. In the opposite direction the offender may neglect you and the family all together. Dont put to much emphasis on this activity unless you notice extreme differences.

Some additional things you can do are:
1. keep track of mileage on the car your partner drives.
2. Get a hold of some receipts if you can. Gas receipts can be good because if your spouse is getting gas at gas station across town you can see that. Receipts for lunches, dinners, gifts that you were aware of.
3. You can always just ask them. Communication can be an excellent tool when it comes to discovering and dealing with an affair. Just be honest, say, hey is there anything wrong you seem distant lately. You get the picture. Take head of responses, defensiveness can be a sure sign of guilt. Turning things back on you by asking you questions or getting defensive are also signs that something is awry.