In addition to the fine advice above, make certain you are fully advised of each other's financial standing (i.e., debts, credit cards, spending habits). One checking account or two? Separate savings accounts? Roth IRA and 401K contributions?
Do you want pets or no; if yes, a dog? a cat? fish or rodents? (It's important going into marriage to know this)
Interior decorating preferences: wallpaper or paint? Pastels or bold colors? Clean line furniture or over-stuffed? Wood furniture or upholstered.
Household chores: who will do what.
Oh, and there's this. It may not seem like much at this point in your lives,
Navigator, but knowing ahead of time which side of the bed one prefers to sleep can resolve any issues later. Also, closet space for hanging clothes can be an issue as well.
I knew one couple who ended up with 2 coffee makers because they preferred different brands of coffee, and neither was willing to give up their preference.
Besides financial, the little aspects of our lives can cause more problems in a marriage than major elements.
Oh, and never ever let the sun go down without resolving differences. (In other words, never go to bed angry with each other!)
And above all, love our Lord and place him first and foremost in your marriage!