Marriage is a mystery
Marriage is not something you can say you've prepared for before going into it because it might be what you did not prepared for awaits you eventually. Marriage to someone can not be predicted until you witness and experience it your self. Yes, you might go for counseling or even seek advice on what marriage is like but your own marriage and home can't never be thesame as someone else. All those counseling and all are just about predictions which might not work.
That's is why the most important thing you need to get prepared is your mental health. When you're mentally prepared, then you'll be able to adjust to any eventualities. Marriage is like a school where you never graduate because the more you stay in marriage, the more you see and unravel alot of things about your partner. Marriage is not a child's play at all. Before you enter into it, make sure you really want it.