I am getting married next year and here is my advice
1) Get a prenup that states that business accounts and assets are off limits for calculating divorce settlements in the event of a divorce. She won't really balk at this, this is where most divorce cases get hairy, and you can tell her it is for business liability reasons. Which is true. This is a simple prenup and shouldn't start the relationship off on a bad foot by having something that is super strict or explicit.
2) If you don't own a house yet but are planning on buying one, buy before you get married. Whatever you put in as the down payment is yours in the event of a divorce, and any monthly payments you made before you got married.
3) Be careful of co-mingled accounts. Keep some money is an account that her name isn't on. This doesn't mean hide money from her, but it is ok to have accounts with with just your name. Once the money is in there, don't pay for stuff you share, this co-mingles the money. You can transfer money from this to a joint account, then pay for shared items.
Things will vary state by state, but after speaking with several lawyers this is the approach I am going to take. Don't complicate things by making a very specific prenup, most likely won't end well. Just make it exclude business assets and watch out for co-mingled funds, and you should be OK. But if you get divorced you're still going to lose money no matter what. So don't get married if you think it could end this way.
Also, if you do a prenup it needs to be done at least 6 months before getting married and she also needs to have an independent lawyer review the prenup with her. Otherwise it most likely won't hold up.