In many GUIs when I select a section of text and then hit the Tab or Shift+Tab button the selected section will indent in or out.
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You can prefix a number, ie. "2>" to indent two tab stops. Or, you can use ">" to indent once, then "." to indent again (this works even though the block is no longer highlighted). If you go too far, "u" will undo one step at a time.
Another useful command is "gv" to restore the last visual block, if you need to apply a different command.