I have been writing for five years. I do mostly fantasy, with action, and  adventure, with some romance . And I occasionally do scifi. I 
I'm workign on two books right now and update each one once a week. I have had ideas for stories my whole life. For my entire teenage years and early twenties I read watched and listened to every kind of stories I could find. With all of them I studied the the varying plot lines, endings beginnings, character origins, plot devices, etc. I watched for the common themes of these, so I learned which ones people liked, which they didn't, what were tied, what were new. As a writer I have learned that there are is no such thing as new ideas, just simply ones people don't see often, and those rare ones they haven't heard as a whole. I use this and what I learned about about story telling, to craft stories that can be seen as original  but basically they are just taking concepts they know and combining them or using them in creative and sometimes unexpected ways.