How do I push a new local branch to a remote Git repository and track it too?

In Git 1.7.0 and later, you can checkout a new branch:

git checkout -b <branch>

Edit files, add and commit. Then push with the -u (short for --set-upstream) option:

git push -u origin <branch>

Git will set up the tracking information during the push.

If you are not sharing your repo with others, this is useful to push all your branches to the remote, and --set-upstream tracking correctly for you:

git push --all -u

(Not exactly what the OP was asking for, but this one-liner is pretty popular)

If you are sharing your repo with others this isn't really good form as you will clog up the repo with all your dodgy experimental branches.

Prior to the introduction of git push -u, there was no git push option to obtain what you desire. You had to add new configuration statements.

If you create a new branch using:

$ git checkout -b branchB
$ git push origin branchB:branchB

You can use the git config command to avoid editing directly the .git/config file:

$ git config branch.branchB.remote origin
$ git config branch.branchB.merge refs/heads/branchB

Or you can edit manually the .git/config file to add tracking information to this branch:

[branch "branchB"]
    remote = origin
    merge = refs/heads/branchB