You wil have to research.
I suggest dividing it into parts:
1) Understand the cliches and where they come from.
As the saying goes, where there's smoke, there's fire. Where there's a cliche, there's something true. It simply isn't as universal and normalised as the cliche makes you think.
One of the cliches I most hate is the one where the couple who like one another are constantly fighting and claim to hate each other. Everyone knows, however, that deep down they love each other and will get togeter.
From my experience, this cliche is somewhat true in children. Say Sam likes Julie, but he's too young to understand his feelings or to express them, so he picks on her to the point she hates him.
Younger teenagers who don't know how to express their feelings may also resort to teasing, which can slide into word fights.
When a couple simply enjoys teasing each other, that is usually done in good spirit and they don't intend to hurt the other's feelings.
Now that you understand the origin of the cliche, you can avoid it while still using the the little spark of truth hidden inside it.
2) Look for romantic advice
There is a lot online about how to manage one's romantic relationship. Some of it are clichés. I would advise you to focus on things like 'conflicts within relationships and how to deal with them', but do try to read different sites, as some offer complementary advice.
Another important point to research is 'toxic relatinships', including red flags and how to get away from such people. This is particularly important because some of the clichés in romance are nothing more than a lot of toxic behaviour, some of which are particularly destructive for a person's mental health, identity and ability to control one's own life.
There are more things you can research - different ways of feeling and expressing love, how one's personality impacts the way you act with your partner, how opposites attract (and also how it can make a couple drift apart), and so on.
Keep in mind that you should never limit your research to simply one site. Go for at least three as the absolute minimum.
3) Keep it real
Most advice is given in terms of generalisations and ideals, but people are individuals, and they are not perfect. Even the best matched couples sometimes do nasty things, and that does not mean they have a toxic relationship. Sometimes a couple spends years (or decades) slowly working through bad relationship habits. Sometimes those habits are uprooted (rarely all of them), sometimes they aren't, and sometimes they worsen. Sometimes those bad habits start as nuisances that will grow into toxic behaviour, and sometimes a couple will break up before it gets that far.
Again, each case is a case. Read through forums and learn about the hurdles real couples faced. See how they reacted, if they fell or if they overcame it. Notice how people felt when they were the targets of emotional and psychological violence.
Though I'm sure everyone knows it, I'll still say it: do not use the real life examples for your own stories, but use them simply as guidelines and inspiration.