It is important to understand where your spouse is coming from, as an indicator of what you might expect in future. If you don’t have this information and understanding it can create all kinds of issues. Someone from a large and gregarious family would have difficulty understanding the solitary nature of an only child, for example.
One of the most difficult to negotiate is financial disparity. If one partner has never had to consider costs, it is very daunting for one who has had to count every penny twice, and it can create great friction if one spends without thought while the other tries to save for the future. Even simple things, like what kind of food you are used to, or what clothes you wear, can be difficult to sort out. If previous romantic relationships are a possible item of contention, they need to be discussed openly or else both agree to pull a curtain over the past and NEVER refer to them again. But this is much easier said than done, especially in moments of stress, when either one is likely to use the past as a weapon. It is essential to sort these issues out before marrying, so that neither has a wrong impression of the other’s expectations and needs. And it can take a lot of negotiation and willingness to be more considerate of each other and to be prepared to compromise. If you aren’t able or prepared to compromise, either postpone or cancel the wedding, because this situation can be a marriage killer.