Your story must be set in contemporary times. This means the exact date is not important. It can be slightly in the past, or the present or the very near future.
Some think anything after the 1950s counts as contemporary. While that is true when one considers the whole gamut of human history, our target audience was probably born a bit later than that, so we are looking for more up-to-date settings.
If your novel talks about specific technology or events, then it might not be contemporary. Mentioning the very latest ‘Nokia 3345’ may seem modern in 1993, but if that phone went out of production 10 years ago, then that fact would date your novel.
Look around you – the world is full of technology. Your hero may have a phone. But avoid terms like ‘smartphone’ - just assume phones are smart enough for your novel. Only if the hero has a antique phone for a good reason would it be necessary to mention this. You can assume he has a tablet, but avoid saying ‘iPad 2’, unless the exact age is very important to the story.
The opposite problem is trying to go futuristic. “Mindy stood silently in her hover-boots” or “Simon adjusted his wrist-tablet” are phrases that move your novel from contemporary into science fiction.
The formula is: “Boy meets girl. They have struggles. They overcome them. Love wins. They live happily ever after.”
It’s all about the relationship between them. It has to be a relationship the reader would aspire to.
The variants are: Someone meets someone. The word ‘someone’ could mean more than one someone, but please don’t confuse us.
Since this isn’t science fiction, none of the characters are aliens. The one in the mental asylum can think he’s an alien, but this is never (positively) proven.
No-one is a vampire – that’s Gothic Horror.
There may be sex, but if it goes on for pages and pages, then it might be better suited to the Erotica section.
Too much “sighing” and “staring dreamily into his eyes” might be better suited to Woman’s Fiction.
Romance always turns out well. The classic tragedies may leave one deeply moved, but we expect our protagonists to walk away together hand in hand - or at least with each other’s twitter handle - and the chance of a second date.