I agree with these suggestions, and I'd like to add to #1.

Get away from your usual place of work. If you can go to a place such as a library, empty office space, or school campus you'll be more focused. These places should be a bit unfamiliar so you're not as comfortable there. Don't think this applies to everyone, but I have seen it work well in my situation.

I have to admit I sometimes find myself in the same boat as this post and I'm always looking for ways to improve productivity.