If you have just performed a change and you realize you want to immediately
do it again, you can hit . instead of retyping it. This is a good way to
quickly repeat simple changes.
For instance, if you are adding indentation to a code block with >, you
can estimate the number of indents that need to happen and type 3> or you
can indent once and then hit . for additional indentation until you reach
the right level of indentation.
Check out the docs for more details: :help .