First, start with a main character your target audience will identify with, namely someone in their early to mid twenties who is either just out of college or just about to graduate at the beginning of the movie.
As our movie begins, have some profound but mundane personal tragedy occur to them. Someone they know dies, a long term relationship breaks up, they lose their job, they do something crazy in a moment of uncharacteristic extreme emotion that completely derails their life. It has to be something that your audience can identify with, so keep it realistic.
The unrealistic, possibly science fictional or magical realistic element will come in later.
During or after the mundane personal tragedy with which you open your original indie movie, you show your main character’s mundane, crappy life. Their crummy apartment in the city, their weird roommate, their colorful but believable friends and/or co-workers, their jerk of a boss, maybe a parent or two.
The idea is to paint a portrait of their lives as being just like your target audience’s lives, so the movie will feel like it is really about them. To this end, work in themes of not being able to get a job with your impractical college degree, feeling alienated in a world that you don’t get and who doesn’t get you, and if possible, work in music from your friends’ indie bands and references to whatever graphic novels you like.
Once you begin to need to have a plot, introduce your unusual, magic-realist element. This not only provides a hook for what otherwise would be obviously just another indie movie, but keeps the audience interested while you slowly work through your basic romantic plot.
Yes, your breathtakingly original indie movie that Hollywood could never make because they are too busy making the next “talking animals make poop jokes” classic will, in actually, just be a standard romance movie in different clothes and locations.
But first, you need that hook. It will have to be something strikingly odd and visually arresting that your main character, in order to show how cool and indie your movie is, will treat somewhat or entirely casually, like this is odd but not big deal.
Also, it should be something with a really obvious metaphorical nature. Your main character feels abandoned and ignored? They discover they can disappear into a magical realm where they are important. Betrayed and disillusioned by someone turning out to be a much worse person than previously thought? They discover they can now see the hidden demons that cause all the evil in the world.
Things like that.
Oh, and don’t worry about firmly establishing whether this is really happening or whether it’s just the main character losing his or her mind in a particularly cinematic way. Your audience will interpret your creative laziness in not making up your mind either way as carefully chosen ambiguity that shows how much you respect their intelligence because you are not spoon-feeding them the answers, but leaving your audience to make up their own minds about how real it all is.
This excuse has worked for at least fifty years, and shows no sign of wearing out, so don’t worry, you are covered.
As for the plot, if you have seen even one romance movie in your life, you already know exactly what the plot arc will be. Your main character meets someone, falls in love with them, they grow closer through most of the arc of the film, then near the end, there will be a sitcom style misunderstanding that drives them apart and prompt your main character to have to do a big grand romantic gesture, often referencing lots of little details from their relationship as shown up till now (“I checked every store in town for that brand of dental floss you said you liked, and when I finally found it…. I bought the whole case!”) in order to make your audience go “awww!”.
This romantic gesture will not seem to work at first, in order to drag out the tension that once extra beat, but then it will totally work, and the film will end with our two lovers finally totally getting together, for real, with an implied happily ever after.
Oh, and because your indie movie is “realistic”, you will need to sprinkle in some “realistic” awkward moments in the relationship, you know, like the ones you never see in movies, assuming you haven’t seen anything made after 1960 or so.
Oh, and to prove your indie cred, be sure to use as much weird cinemetography and unusual editing choices as possible. Track from a rooftop conversation to one on the street below. Have your character fall out of a window and land in bed, asleep. Why? Because you’re outside of the box, man! You’re free! You can do whatever you want! So you’re obligated to show everyone that you know it and give the film school types something to babble on about in their faux-industry lingo.
Well there you have it. Throw in some hip pop-culture laden comedy for your comic-relief everybody but the two leads, a B plot line for whatever character seems the most audience friendly, and you have yourself a brand new breaktakingly original, impossible to make in Hollywood, fresh and groundbreaking indie movie.
You know, just like all the other ones you like!