How do you get to regenerate energy faster?

You can not just "regenerate energy faster" unless you are the mongol class in mafia wars.

The only way to get energy faster, aside from using rewards points which is a waste, (you should save for much better things) the only way to get energy is to either level up (gain exp through either fighting more, or as a total catch-22, doing more jobs) the other way, is to get an energy pack. The way you can get an energy pack is either through helping other members in your mafia family on either jobs or gifting, or by sending them energy packs (found on your "my mafia" page) as the icon with the little lightning bolt, and hope they give you one back. Though you should know, that you can only use one a day.