If you suspect, or even discover, that your spouse or significant other is cheating on you, the desire will be strong to punish him for betraying your trust and corrupting your relationship. You may want to do things that will make your partner feel especially guilty, so that ultimately he will end the affair and come back to you. Guilt can be a positive motivator to inspire someone to back away from poor decisions, but ultimately there is nothing you can do to "make" someone else feel what he may not feel. This includes both love and guilt, which leaves you the arduous task of managing your own feelings and actions.
Ask yourself what you will gain out of his guilt. If you plan to stay in the relationship, this guilt could help him make better, more responsible decisions. This is a temporary solution, however. Long-term guilt has a negative impact on all involved. If you plan to leave the relationship and this is a form of revenge, ask yourself how this behavior makes you grow as a person.
Open up the lines of communication so you can gauge his emotions. His guilt will depend largely on how entitled he felt to have the affair, or how he feels about the other person.
Explore his motivations. People cheat for different reasons, and often it isn't a lack of love. He may feel his needs are not being met at home and this new person simply gives him the attention he desires. The more torn he is between you and the other woman, the more guilt he'll feel misleading you.
Work on the problems that may have caused him to stray. If he is feeling neglected, pay him more attention. Without his excuses to justify the affair, the more guilty his lies and deception will make him feel.
Talk about the future. Even though the passion in the other relationship is exciting and new, many people who have an affair don't wish to end their primary relationship. Your expectations will likely put subconscious pressure on him to choose.
Suggest therapy. An affair is an escape --- an escape from you, from his obligations, and from the mundane. Keep him rooted in reality so that he can deal with the reasons he needs the affair in a mature way.
Take responsibility for your own actions. How he acts or reacts ultimately matter little in your choice to either forgive him or end the relationship. Making him feel bad won't make you feel any better. Learn when to let go just for your own sake.