1. Full and complete disclosure of all assets and debts,
2. Free from duress -- do not wait until the last minute to finalize the prenuptial agreement,
3. Insist that your fiancé obtain counsel,
4. Do not sign anything you feel is unfair.
Prenuptial Agreements attempt to balance the business/financial interests of the parties often while the wedding preparation is underway. Better to complete it early so negotiations do not hinder the joy of the pending marriage.
Here is a link to an Anderson Cooper story (note: it should be "counsel"not "council" on the bullet point summary):