A prenuptial agreement is a living, breathing document that can be modified as your marriage progresses. In order to be effective, however, it does have to be properly amended under the law, which can be a hassle. Like anything else in life, you can avoid unnecessary work in the future if you do it right the first time. To find out what couples should absolutely state in their prenup and what the most commonly forgotten details are, we spoke with divorce attorney Louis M. Atlas for his expertise.

If you are considering a prenup, remember to put it together well in advance before your big day. It's easy to get caught up in the excitement of wedding planning and forget about it all together. When it comes time to sit down with your lawyers, avoid resorting to a "what's mine is mine, what's yours is yours"-type of negotiation. According to Louis, you might think you're simplifying the division when you're actually overreaching, which could come back to bite you later. This means that if one partner is significantly more successful than his or her spouse over the course of the marriage, it only helps one party in the case of a divorce. See what other tings you should consider below.

Most Important Things to Include:

• Any property coming into the marriage is your separate property: Specify that your separate property cannot be divided. This not only consists of the property itself, but also any increase in value, exchange from one form to another, or any income made from that property.
• Define marital property: "You can define it as property that is accumulated in both names and separate names are not," said Louis. "Traditionally without a prenuptial agreement, any property acquired after the marriage, whether joint or single, is marital property."
• Gifts between spouses: "It's interesting; in divorces, the little details with emotional value become as important as the high-ticketed items," he said. Again, make it clear that any gifts from your spouse during the marriage are your separate property.

Things You're Probably Forgetting to Include:

• Your retirement benefits: If you have a 401K, an IRA, or any other retirement accounts that you'd like protected during a divorce, be sure to include that information. "State very clearly that after the marriage, any money that gets contributed to that retirement account or pension account, including any increases in that or changes or substitutions, will remain yours," said Louis. "That means that after marriage and if there were a divorce, the prospective spouse would not have right to claim against your retirement account."
• Spousal gifts: If your partner gives you a gift during the marriage that you'd like to keep, list the item as personal property. People forget that gifts from your spouse are generally considered marital property.
• Estate rights: "In New York, for example, if you get married and you don't leave a will, your spouse gets one third of your estate," said Louis. "You can waive those rights in a prenup if you so desire."
• Debt: You can also do the same thing for debt by stating that one person's debt remains their debt and that you will not be responsible for it after the marriage. "With any money that you make, you can mold it however you want to with respect to exclusion of what is going to be divisible should there be a divorce," said Louis.
• Engagement ring: "If you own a diamond ring or have been given a diamond ring as a gift — and presuming the diamond is a real diamond and not a synthetic diamond of no inherent value — this is your separate property to be listed as such in the prenup," said Louis. He also mentioned that listing diamonds as separate property is a trend he's been seeing more frequently in his cases.