Soon after you tie the knot, you need to do a benefits audit. Does it make sense to swap your singles health plan for family care? It may if your spouse works at a company where the employee contribution is very small. Taking the time to weigh the cost of two single plans against family coverage could potentially save you about $400 a year. Do the same for other services, like your cell phone bill. You can also commute together, which may allow you to get rid of a car.
Once you're married, file your taxes jointly. If you don't, you'll lose some big tax benefits—particularly if your incomes are pretty disparate. If one spouse earns $75,000 and the other $15,000, filing jointly can help you save about $1,500 in taxes a year. (If you're not sure about your particular case, ask your accountant.)