Many people who are engaged don't think that anything will happen to their marriage. They might assume that they will live happily ever after. Unfortunately, this might lead them to not plan ahead just in case something does happen that leads to a divorce. Taking the time to create a prenuptial agreement can help you and your future spouse to feel more secure in the marriage.
When you are working on the terms of the prenup, make sure they are fair. The court will likely throw out any agreements that favor one side more than the other. Think carefully about how the terms will appear to everyone outside of the marriage.
Be sure that you start working things out as early in the engagement as possible. Remember that you can't present the document as you are walking into the wedding venue. Your soon-to-be spouse needs to have time to consider the terms of the agreement.
Make sure that you don't anything illegal in the agreement. This might seem obvious, but some of the things you can't include might surprise you. One thing that can never be included is child custody and support matters. Typically, alimony can't be waived in a prenup either.
Some people think that there is an "ick" factor to asking for a premarital agreement. In almost all cases, the agreement serves as protection for both spouses. It isn't an assumption that the marriage will fail. Instead, these agreements are an acknowledgment that things sometimes happen and a way to prepare for the situation before you have to deal with the split.