Now how to get Started?

Hey guys thanks for help on my previous question! Just wondering where exactly should i start in this whole game developeing bussiness? I certainly dont eant to dive straight into the making and coding process! I like to be organised and I was wondering should I start on concept art and designs for the game or writing the story and making plans to work on etc. or prehaps ive missed something that is ultimately the most important thing to start on!

I'm going to start by watching video tutorials on Unity3D and how to start oh and downloading it havent done that yet whoops!

All help is greatly appreiciated and links to related websites and videos are helpful too!

I'm sorry for any grammer mistakes I'm awful at grammer!