Money is a notorious source of conflict in marriage.
As with any other conflict, you will have to practice good communication and problem-solving skills. This means talking through issues at a time when you can both remain calm, listening to each other's point of view, and working together to come up with mutually satisfactory solutions. In addition, for your mutual benefit, it will help if you both practice good money management skills. This means planning ahead, keeping track of where your money goes, and setting realistic spending limits. If you currently have separate finances, each of you should write out your current budget.