Please read the Pro Git book.
To make a branch in the same place as you are in history:
git branch branch_name
to switch to that branch use
git checkout branch_name
you can do both of those at the same time with:
git checkout -b branch_name
to keep alternating between the last 2 branches use
git checkout -
(this is the similar to the behaviour of cd -
)
Once you get better with the syntax of git, use a good branching strategy and stick with it. I use Branch per Feature.