I’m a natural night owl, too. Though, like Jason, I have a young child that I have to be able to flip around to morning hours for, on occasion.
My suggestions are to find good blackout curtains. Amazon sells a great brand – Eclipse, I believe. I think Target sells them, too. At my last address we had a southeastern exposure and my bedroom had direct sunlight all day long. I put up a double rod with a double layer of blackout curtains and it was wonderful. White noise is helpful. If you’re caffeine sensitive, try avoid it too close to bedtime, as others have mentioned.
The two biggest things you can do for yourself are to protect your sleeping hours as much as you can, and keep to a night schedule as much as possible. Unless you have a child at school or a sick relative that someone might need to get a hold of you urgently for, turn off the phone. People have a way of “forgetting” you work nights. If you have a significant other and/or children, keeping a night schedule can be more difficult than if you’re single. Even my four year old understands that mommy needs to sleep late because I work nights though. You just have to learn to schedule appointments later in the afternoon, and meet people for brunch instead of an early breakfast.