It depends on whether you have used other version control before.
If you jump straight to using git in production , you'll experience a lot of "git anxiety" every time you run a command that you're not quite sure what it will do.
There's always the git book. http://git-scm.com/book
Realistically git isn't something that you can just pick up on an ad-hoc basis.
Best way is just to make a folder, fill it with some random text files and type "git init". Then you can practise, just make changes to files. Try branching and merging, try rebasing some commits to a different branch, try cherry picking from one branch to another. Make sure you get some practise in merging conflicting changes because that comes up annoyingly often in the real world (so pick a merge tool that you are comfortable using since git will plug in to a few but the default one is not the most friendly).
You can learn it pretty well from one machine, but it might help to setup a github and use another machine (or VM) to practise the "distributed" part (understanding origin/master etc).
Don't necessarily worry about learning everything from the get go, I have used it for about a year and there's still plenty of features I haven't ever had to use but make sure you understand what you think you understand.
When you are learning you'll find stuff will happen which wasn't what you expected, at this point you can start googling and will probably end up on a stack overflow page that will answer your question succinctly.
There will be times when you think you have broken everything, you probably haven't. At this point git log and git reset are your friends.