Currently for switching to another git commit (on the same branch...actually, on the master branch!), I\'m executing the command
git checkout ea3d5ed039edd6d
The question is a bit vague, but if you want to just change files in your working tree, you can simply do this:
git checkout [commit|branch] -- .
You can then stage the changes and create a new commit if you wish. This is pretty useful sometimes.