Ever notice how movies about great romances end with a wedding? Everything after that, of course, is “happily ever after.”

So what happens when you get to the “after” and discover it’s not quite so … happy?

That’s the question Carley Roney heard from thousands of users of TheKnot.com, the wedding Web site she edits and co-founded with her husband of 13 years, David Liu. Many readers stuck around long after the nuptials and started asking about new things: buying a house, dealing with in-laws and starting a family.

So Roney and her staff founded another Web site in 2005, TheNest.com, focused on post-wedding issues, and followed up with a book, “The Nest Newlywed Handbook: An Owner’s Manual for Modern Married Life.”

The book covers a lot of ground, including managing money, decorating together and dividing up housework. The key, says Roney, is effort: doing the little things — like choosing the movie your partner really wants to watch — that show you’re not taking each other for granted.

Here’s her take on some of the problems couples face.

Q: What’s the biggest issue facing couples when they first get married?

A: The big issue is always control. People are getting married a little bit older; they know how they want their dishwasher loaded and what their style is. It takes a little negotiating and it sort of pervades all different aspects of life. The most prevalent [conflict] immediately is household control. You look at the socks on the floor and think to yourself, “Are those socks going to be on the floor forever?”

Q: What about in-laws?

A: We all have certain expectations about what family’s supposed to do and how family’s supposed to behave. They can crush you with their interest in your life because they see you slipping away into adulthood.

One of the biggest problems we see is, “since they’re family, I can just take it up with them myself.” That’s a really bad idea. … With the parents, too, there need to be some priorities and boundaries. The final rule is, you’re not allowed to dis the other person’s parents, even when they do.

Q: Experts say most marriages break up over money. Any advice?

A: You have to figure out people’s different financial priorities. What kind of approval processes does one have to go through? If I spend $25, do I need to tell you?

Everybody needs some financial privacy. Everybody needs their own “mad money” that they can spend, no questions asked.

Q: Are religious clashes as problematic now as in previous generations?

A: They become more problematic around the holidays … And I think that also ties in very strongly with the in-laws. It certainly is an issue if one person is much more observant than the other. You have to respect where the other person’s coming from. If you want to go [to services], you go. Just because you’re married doesn’t mean you have to do everything together. You’re not one person.

Q: What about friends of the opposite sex — can you keep them?

A: Are they truly just friends or are they secretly pining away for you? Our rule is, if it makes the other person uncomfortable, you simply have to do something about it. If it makes them uncomfortable, it’s not fair.

Single friends are a whole other issue. I know my husband was like, “Oh good, we’re married, we don’t have to go out anymore,” and I was thinking the party was just getting started. All of marriage is in the art of compromise. Maybe you can say, “You’ve got to come out with my friends one night a week, but I’ll spare you the other nights.” Don’t give up something you really love and then secretly resent it.

Q: In the book, you talk a lot about how to fight. Can fighting be healthy?

A: We get people in the book to understand what kind of fighters they are. It’s going to be very hard to get someone out of their habits, but at least if you can understand and then come up with some ground rules … If one person doesn’t mind slamming the door and walking away but the other person is petrified, you need to address that. You really do have to have some clear boundaries between you that nobody will break.

So much of it is being self-aware. You’re usually really fighting about something totally different than you’re bickering about. It’s because your feelings were hurt or you’re protecting your pride — if you can really see more of the underlying things, it might get you to say, “Let’s stop” and say, “I’m really hurt. I’m not mad, I’m just hurt.”

Q: What’s the secret to a long and happy marriage?

A: It’s about putting the other person first. It’s the hardest possible thing to do. And you can’t do it in a 1950s-housewife-ignoring-yourself kind of way. … It comes down to a sense of truly understanding and caring about the other person.