1- Do not put pressure
Living an outer couple relationship should not oppress you. Rather, it should thrive. Remember the reasons that led you to look elsewhere.
2 - Cultivate the secret
Few people admit having a dual relationship to their spouse and few spouses actually accept this type of relationship. Keep in mind that your married life should in no way interfere with your life in an extra-marital affair. Some also say that the success of an affair lies on the secrecy that surrounds it!
3 - Opt for distance
Avoid all incredible situations so that lover and spouse do not intersect. Remain the only link between them.
4 - Find good alibis
Car breakdown, a meeting that ends late, business lunch... select your alibis carefully. A small tour on the web and you will find many companies willing to use tricks in order to save you.
5 - Go wild with desires and pleasure
In a word : ENJOY