Well, first, you must find someone that is the complete opposite of you. It does not count if the person is outgoing when you're shy. The person has to be the opposite of you in a way that defines you. They have to be opposite of you in a way that's culturally taboo.
You're poor and they're rich in a community where money is everything. They're white and you're black and it's the 1950's. They're heavily involved with the Steelers and you were a fan of the Seahawks. The characters are opposite of each other in a way that makes up their identity.
You also need an orchestra to play slow piano and violin music, especially at the introduction scenes.
It does not matter if there's actual chemistry there or not.
First off, you have to have a few mindless drones as friends. They're either used to serve as comic relief, to amplify the differences between your target, to further elaborate on why you can't have your target, or sometimes, they're just used to introduce you to the opposite person.
Well, after said friends introduce you to each other, or you guys accidentally stumble upon each other by clumsiness that you both instantly know is fate, you have to challenge each other.
Normally, the boy will say something like, "Well, you don't eat a lot, do you?" The girl will defiantly say, "Well, I do eat a lot!"
It never comes easy. They reject each other a lot. Of course, this is the prelude to the guy getting the girl into doing something. The objective is to get the person you're with feeling that they're insignificant as a human if they don't do what the the other person says. In the case above, it was getting the girl to feel not human if she does not eat, so she has to prove herself.
Some love movies just skip this scene and get straight into what will serve as a problem later on in the movie.
The guy and the girl enjoy themselves, but somewhere along the way, one of them finds it nice enough to declare, "Well, I'm seeing someone." The other one responds, "Are you even in love with them?" "Well, of course, I'm in love with them! How rude! We're getting married!"
They run into each other all the time. Most people would assume that someone is stalking somewhere, but for some reason, it never occurs to the minds of our protagonists. They have something about themselves that separates them from their friends. I'd like to say it is normally a lack of a brain, but in Hollywood's case, it is normally something as subtle as a favorite band, the same type of glasses, or the same kind of dog.
This item normally builds conversation, serves as symbolism later on in the movie, or foreshadows a future event. Once they identify they have that "item" in common, the two are absolutely sure they're going to get married.
During these scenes, we normally learn of the character's hobbies, too. It seems there is more than what we originally judged to these characters. Joe likes to bake. Jenny likes to eat.
There's always a dancing scene somewhere, or the mentioning of a dance. One of the characters might casually mention that they can't dance, but the other person always has skills when it comes to dancing.
Somewhere between all of this they have the passionate, gratified sex scene. It might start from Jenny saying, "Oh, hey, I find the sound that the spatula makes as you smack the hamburger against the stove very hot. Oh, how it sizzles like my love for you!" In a lot of movies, somehow the characters mention that it is their first time, or they might not end up having sex for years because that one night is so great.
After we go through the "happy hour," that is when the climax comes in. We find out that somewhere along the lines someone's family disapproves of the relationship. We find out that Joe is engaged, magically in love with Jenny, and perhaps, the other person finds out. Someone might have a disease. Someone might have lied about their identity. In some cases, Joe walks in on Jenny making out with Steve, who is Joe's enemy, and it is all a big misunderstanding that causes them to break up.
This is normally when the mindless droid friends come in. They're normally good at delivering news like that.
This is also when the keyboard music and the violins get the most dramatic. Sometimes, there's a "goodbye" scene. It normally is light and intimate like kissing in the rain.
On the other hand, the "fight" scene is where Joe can't bake, Jenny can't eat, and everything that they hate about each other is revealed while they're tossing stuff at each other. Any items that reflect the "happy hour" scenes normally get broken or left behind in this part of the show. Joe mentions that Jenny never liked him because she never prided herself on watching him bake his favorite cake. Jenny will say that Joe never loved her because Joe never found out what it was she ate before they meant that fateful night. For all these reasons, it just is not meant to be.
In some cases, years go by, and the characters still retain passion for each other, but they date others.
It normally varies, but it all relays the same message: they can't survive without each other because of the five days they dated.
Sometimes, a third person is thrown in. One of the characters ends up in love with another person. The other character may soon follow, but it is often that they don't. By "fate," Joe and Jenny stumble upon each other. Joe or Jenny might be passionately in love with another person, but they leave the other person that they've known years for someone they dated for five days. The other person's emotions aren't normally considered. The “other person” normally understands the emotions and logic behind it, even though that Joe is normally getting married to them within a week.
Joe and Jenny end up together. They either live happily ever after or one of them dies. Joe finds out what Jenny ate before they ate. Jenny watches Joe make his favorite cake.
If you follow that formula, you can live a love movie. If I'm forgetting something, let me know.