I found the best way for me was to keep the same hours on my days off as I did when I worked. If this isn't possible for you then you could try this. On your days off, when you get off at 7am, stay up all day and go to bed around 8 or 9 that night. This would make you sleep all night then wake up the next morning. That way you will be awake during the day and sleep at night. It's a bit rough when you first start it but I have some friends who work night shift and that's what they do. Also when you work the night shift it helps to sleep in a dark room durning the day. Use blackout shades or towels over the windows. I listen to a artist called Mars Laser. He has a very relaxing music, I listen to Moonlight when I sleep. It helps me sleep a lot better.
Keep the same hours every day of the week and do not try to change to day on your off days. Stay up for two to three hours later than normal so as to reach your desired bedtime and this should be gradually. Also do not eat dinner before bedtime but instead have a light meal and try to take the biggest meal first then during your lunch break eat a sized meal.