1. Don't pretend it didn't happen. Discuss it and examine it. Often times the tamping it down and pretending it never happened actually turns into something akin to putting a lid on a bottle of soda, and then shaking it. When the lid is remove, and explosion happens. So, don't play like it never happened. If you do, anytime anything looks at all suspicious you will overreact. Instead, address it, discuss it, and examine it as much as you need to.
2. Get your questions answered. Most people whose spouse has cheated on them have one burning question: WHY? Get that and any other question (within reason) answered so that you feel comfortable and content again. Often the questions and the not knowing are worse than the actual knowing. It can be embarrassing for both parties to share details, but it can also leave little room for the wild imagination to exaggerate and make worse of the situation. Your mind can make you crazy if you let it, so ask your questions, don't ignore them.
3. Don't turn the relationship into a punishment. Look inside and determine what you would need to start fresh, and feel any semblance of trust. When in a relationship that has suffered from one spouse being unfaithful, the other spouse needs to make a decision. They have to determine if they can give it their best effort to "forgive and forget" or if they are going to constantly try and hold it over the other partner's head, or make them feel guilty about it. If you can't try and start at a clean slate, you are dooming your marriage or relationship to even more complication and pain.
4. Work on building trust, but give it time. You can't expect instant results. After a spouse has cheated, trust becomes the biggest obstacle. The spouse who was cheated on often feels insecure, unloved, and unhappy. So, to make a marriage work after cheating, it will take some time for wounds to heal, and insecurities to dissolve. Work at the trust, and love each and every day, but do not give up just because the results aren't instantaneous. They rarely are, and it will be difficult, but it helps to recognize before hand that it takes time.
5. Be honest with each other and yourself. You have to be able to say, "You hurt me." Or "I strayed because I felt ignored." Or whatever the reason may be. The point is, if you can't be honest with one another, it will be a hard problem to recover from, as cheating can leave a lot of insecurities, wounds, and distrust. Honesty is critical to getting back to a good place.