Depending on how many remotes are present for your local repo, follow the appropriate flow.
Checkout a remote branch workflow:
For repos with one remote:
If your local repo is having just one remote for example just origin:
git remote -v
origin https://github.com/my_username/AwesomeRepo.git (fetch)
origin https://github.com/my_username/AwesomeRepo.git (push)
Then you can simply do:
git fetch
git checkout some_branch_name
For repos with multiple remote:
If your local repo is having multiple remotes:
git remote -v
origin https://github.com/raisedadead/wiki.git (fetch)
origin https://github.com/raisedadead/wiki.git (push)
upstream https://github.com/FreeCodeCamp/wiki.git (fetch)
upstream https://github.com/FreeCodeCamp/wiki.git (push)
Then you have to specify a remote as well:
git fetch
git checkout -b some_branch_name <remote>/some_branch_name
where <remote> in this example is either upstream or origin.