Since I started to write I've learned that there're a few ways you can go about it. I've read and watched a few interviews on how the 'famous' authors approach their work. At a charity event in NYC John Irving told the audience that before he begins writing he needs to see the end, he said it can take him a few months to figure it out and then he'll work from there. On Charlie Rose I’ve heard Stephen King say that he doesn't necessarily know where his characters are going to take him, so there really isn't much planning in his approach. I'm a bit of a mixture I guess, but when I sit down I tend to work the same way King does, the story seems to just unfold through the characters, as for the end most of the time it wraps itself up. However,  I've started with the end with a few stories, I guess it all depends on what  kind of idea pops into your imagination. There is no right way so just have fun! LOL