Is it possible to build your credit up quickly?

[Sam Huntley]

Hi, I'm looking to jump back into investing after ****ing up pretty hard about a year ago. I didn't lose all of my money but I definitely hurt my credit. I'm at a 600 and was wondering how to raise it as quickly as possible. I hope I'm not being too naive in thinking I might be able to fix it up within three or four months but I figured I might as well ask you guys. 

Thanks as always!