Make sure you are truly ready to be faithful and committed to your marriage before attempting to rebuild trust. Nothing is more devastating to a victim spouse then learning to trust a person only to be betrayed again.
If you have decided to rebuild the relationship, stick to this decision. Avoid language that indicates that you are uncertain about your ability to continue the relationship in this state; doing so may only cause your spouse to shut down and keep their emotions to themselves out of fear that they will lose you or you will seek greener pastures again. Nothing can be more dangerous to the recovery process during this period, as bottled-up feelings will eventually burst forth and perpetuate these problems. Create a safe environment in which your spouse feels free to express their feelings without fear that doing so will cause you to leave.
Do not, do not, DO NOT allow yourself to appear irritated with your spouse when they bring up their feelings or questions about the affair. This irritation is natural; people do not like to be constantly reminded of things they are ashamed of, and it is easy to turn this shame into annoyance at your partner. The victim spouse, however, has a clear right to these feelings: you are most certainly in the wrong, no matter what your reasons, for undermining the sanctity of your marriage, and holding yourself accountable for your mistake is a necessary part of reconciliation. Irritation will not only anger your partner, but will depict a lack of remorse and ultimately convince your partner that you are not "with them" and are likely to cheat again.
Playing off your affair as "it meant nothing" is not the best course of action. Be truthful about your reasons, even if you think those reasons may hurt your spouse. A spouse who cheats for no good reason is a spouse that has absolutely no respect for the marriage, and it sends a message to the victim spouse that they have no reason to trust you again, ever. Explaining to your spouse that you have cheated because of emotional trauma - such as being in love with somebody else or out of fear and self-destructive tendency - gives your spouse a handle on which to understand your affair and regain their trust in you.
NEVER tell your spouse that "you don't feel like talking about it right now." In all honesty, you gave up your right to discuss things on your schedule when you betrayed your spouse. Putting off discussions that are important to them only ensures that these concerns will grow like cancer in the meantime, and "later" may be too late.
Do not allow your own feelings to eclipse those of your spouse. In all likelihood, you are dealing with emotional trauma of your own - your guilt for having the affair, your shame at what has been discovered about you, even the loss of the lover if you have decided to choose your marriage instead. It is important that you deal with these feelings, and even share them with your spouse. However, do not allow yourself to fall into the trap of ignoring your spouse's cries for help because you are too preoccupied with your own struggles. If you have decided to make your marriage work, it is important that you dedicate the necessary time and attention to your spouse.