Something I read a few years ago has made a lot more sense over time and has proven itself true also (and I expanded on the theory a bit). Regardless of how much you do or do not have in common, there are 4 main things you need to be on the same page about: MONEY, RELIGION, KIDS, FAMILY. Opposites attract, but so do like minded people. Couples can have a bunch of interests in common, or hardly any, and either can work as a model for a successful relationship, so don't judge the potential of someone for a relationship based solely on the smaller likes/dislikes eg. I like rap and she likes pop, I like comedies and she likes dramas, etc. 4 of the biggest things that help guide multiple factors of our lives are the things mentioned above.
Money: Number one reason couples divorce. You need to be on the same page in regards to, how to save/spend, should we or shouldn't we invest, home ownership, credit, pension/retirement etc among a whole host of other money questions. If you got one person that's reckless with the funds, while the other one is being responsible and saving towards something for the better of both (home/car/retirement) then there is going to be major friction. Or if someone is giving their S/O money all the time because that person isn't good with their own and end up spending it all, serious problems(resentment) will arise.
Religion: I can't even touch too much on this because I'm not that relgious. But that being said, religion (or lack of having a religion) is a HUGE deal for a lot of people. Considering it can guide your moral compass, cause you to act or believe in certain principles etc it only makes sense that both people should be on the same page about it. It will also determine if you get married or not, and if so, how you get married. Considering getting, or not getting, married is a big issue for any long term relationship, being on the same page regarding religion will help with that decision when it is time to be made.
Kids: Do you want them or not? Lowkey, this might be the biggest factor out of all of them. Communication can help to solve some of the problems present in the other categories, however, plenty of people have broken up over kids. If someone wants kids, and the other person doesn't, its a wrap, no ands ifs or buts about it. But it's more then just determining if you want kids or not either, you gotta dig deeper. How many kids do ya'll want? Boys or girls and are you okay if you don't get your preference? Is adoption an option? What if your baby isn't healthy, can you and your relationship handle the exta stress of raising a special needs child?
Family: This was my own addition to the list I had read, because family is a huge factor in most peoples lives (even if their absent, that lack of family helped shape that persons views etc) so I thought it warranted a spot among these things. When I say family, I don't mean if your SO and them get along (although that is a bonus), but how much power/influence does your SO's family have over them? You can never, NEVER, turn your back on your mom's and pop's and prolly a few other select family members. BUT ultimatly if your in a commited long term relationship like a marriage, at some point your families advice on things stops being gospel and needs to become suggestions. Think of it in bigger problems ie raising the kids. You wan't to raise them one way, but your SO still lets their family influence their opinion on this heavily, so while you think one thing (and know that they probably think that too) their arguing their families position on it. Once your adults, you need to realize that family means well, but what they say or do is something to take with a grain of salt, because all of our family members are human and all humans make mistakes. Nobody has it figured out. But some people stay on that mom and dad know best tip for life, even though at some point you have to realize that, even though what mom and dad do/did and say/said worked for you, what they did wasn't perfect and there's room for improvement. In a way this point is in clear correlation to the other categories, because family will be the most opiniated and give the most advice on the above 3 things.
