CNN/Money gives the short guide (5 tips) to prenups.
Lewis Schiff writes (excerpt):
Ensure that it’s needed. Sit down with your spouse-to-be and outline exactly what each of you would want to accomplish with a prenuptial agreement. State laws already cover how property is divided during divorce, so it usually only makes sense to have a prenuptial when both parties want a different outcome.
Get legal assistance. Prenuptial agreements are legal, enforceable contracts and the laws governing them vary from state to state, so this is one time you should not try to do it yourself. To ensure an agreement that addresses your particular needs and is fair to everyone, each party should consult with their own family lawyer.
Make full disclosure. Both sides need to disclose all of the assets and liabilities they are bringing to the marriage. Failing to so will usually void the agreement. You’ll need to consider
Keep it strictly financial. Courts will only uphold agreements that are monetary in nature. So don’t try to sneak in anything about requiring your future spouse to take out the trash every week.
Plan ahead. While there’s nothing to stop you from drafting this kind of agreement after you’re already married, I recommend doing it before — when you’re madly in love and have your partner’s best interests at heart.