How do I make more space on a Macbook air? I have a bunch of files that I don't need. I'm wondering what's taking up all the space. I am tempted to almost format the laptop and start fresh.

What can I do to find out what is taking up all the disk space in my Macbook?
I suggest using a tool like Space Gremlin to identify files eating up your disk space. 
https://itunes.apple.com/de/app/space-gremlin/id414515628?mt=12
http://www.spacegremlinapp.com/