This seems missing from the other answers, so I feel the need to emphasize it here...
Craft does not require .dev for local development.
Your local URL can be anything you want, Craft does not care. There is no requirement whatsoever on using a
.dev domain. That being said, it is recommended that you use a "dev-sounding" URL, in order to avoid the licensing nag warning. And even if you're getting the warning, it won't have any negative impact on the capabilities your site.
The other answers already address what to do if you do use a
.dev URL, so I won't cover it here. You may also want to read this helpful answer on a related question.