Set a budget
A budget can go a long way toward not having money problems. Most money problems come from the stress of too much debt, or overspending. Having a budget that both parties stick to well can eliminate the blame game, and allow everyone to realize that while money problems happen, that you are trying to be wise with your spending, and not careless. In addition, a budget can allow you to allocate some money to each person individually so that there is some personal control over money that won't affect the shared holdings (such as your ability to make your house payment). Set your budget, review it regularly, and check up with one another to help motivate yourselves to stick to it.

Have defined money rule
One of the best ways to avoid money problems in relationships is to have a clearly defined set of rules attached to your money. For example, you may not want your spouse to call you about every purchase they wish to make, but purchases over $50 may warrant a phone call to ensure the other party does not object. That would be a great defined money rule. Another money rule might be that you do not buy anything on credit. Another money rule may be that 10% of what you earn goes directly into savings. You might then have rules attached to that savings, how it is used, when it can be dipped into, etc. The more defined the rules, the more difficult, or blatant it is when you break them, and thus the less likely you are to actually do so. Thus, fewer problems will occur.

Prioritize
No one ever has enough money for everything they want to buy, so part of avoiding many relationship problems is to prioritize your money. For example, you might set "getting out of debt" as your biggest priority. Thus, buying clothes, vacationing, eating meals out, etc. are not to take place until that debt is greatly reduced or eliminated. On the other hand, "enjoyment" might be your first priority, etc. Knowing one another's priorities can help you avoid ignorant mistakes that lead to relationship problems about money. Sometimes it is simply a matter of misaligned priorities. She might feel like he is spending carelessly because he bought lunch out, and she brown bagged, but he might feel she is trying to squash his ability to feel good about himself by forcing him to live like he is impoverished even though he makes a good salary. The point is, unless you talk about it before it happens, it can cause relationship problems.