Git fetch remote branch

Question

I am my co-worker are working on the same repo but in a different branch that is for different projects. But my colleague wants to pull a branch specifically, How do we do that actually? 
Git cloning the repo doesn't seem to work. When I created the branch, I did -b checkout. Does that affect the result with git cloning?

$ git branch -r
origin/HEAD -> origin/master
origin/daves_branch
origin/discover
origin/master

$ git fetch origin discover
$ git checkout discover

I executed these commands but didn't seem to work. What I want to do is to check out the branch and then commit back.