So I started writing a romance story, but I don't knowmuch about romance. I was wondering what would be the best way to for a sweet and simple love story.

You should do some research using shows,books,movies;etc. Taking what you see and creating what you think you'd enjoy reading will be easy.

There are blogs that can help you out with your writing through advices about characters, plots, relationships etc.

http://writeworld.org/toolbox
http://referenceforwriters.tumblr.com/

But personally, I guess romance is much more simple that you think. Someone could have a crush at the bus stop - be attracted by his/her's appearance, style or likes (having an accessory of something that you love). Or the love could grow slowly, like you're falling for someone's secrets - their way of thinking, how they are when they're comfortable, making jokes and everything.

Either way, good luck with your story!