It takes a long time to get used to flipping your biological clock from days to nights (then back back again when your off). Some folks never get used to nights, and can't do it. Give it some time.

Eat well-avoid fatty "comfort"/fast foods on the overnite, they'll put you rite out. Some are just nasty (health wise) in general anyways.

Ease up on the caffeine intake-especially four to six hours before you want to sleep.

Some folks sleep in one lump (just flip from sleeping at night-to sleeping in the day). Some take a few naps during the day, one being of a few hours length. I sleep a combination of the above, depending upon what I've got going on.

If I'm working a lot of hours (overtime/extra shifts), I get by with what sleep I can get. The "reward" is the pay, knowing that I suffered-I use it wisely.

If your job/position allows a catnap(s) it can work wonders. A 15 minute power nap, on one of the overnites when I have a lot of stuff going on during the day (a "nap" day), comes in handy. I can get everything done, AND not be a zombie.

To sum up: Give it (nights) some time. Ease up on the caffeine. Get into a regular sleep schedule, fiddle with it within reason. Get into a regular meal pattern (avoiding heavy meals before sleep).