How to come up with stories?

Just so you guys know, im not asking for you guys to give me a story plot or anything. I realy love to write and at the moment im having trouble tryng to think up plots for a story. i like the supernatural books like Sookie Stackhouse Series. but at the same time, i also like writing romance novels. but it seems that every idea that pops into my head ends up being from a book that ive read. i dont wanna end up copying another authors idea or anything. so can you guys plz give me some tips on how to think up plots, themes, and characters for stories? im not asking for the actual idea. just tips on how to think of the idea