It all depends upon your last meal. My meal size isn't perfect - 450 cals per meal (or however large the meals) - mine fluctuate, but not too much. I'm more hungry more quickly after an apple and a carb bar than after eating basically the same amount of cals (maybe a bit more) of chicken and rice. My meals are spaced out like so:
4 am - pre-workout shake (925 cals)
6:30 am - post workout shake (400 cals)
9:30 - 10:00 am - 2/3 of Kong bar, 1 apple (400 cals +/-)
12:30 - 1 pm - lunch chicken, rice or something similar (500-600 cals)
3:30 - 4 pm - protein shake (w/water) and chicken breast (400 cals)
6:00 - 6:30 pm - dinner - chicken, fish, wheat pasta & veggies (500-600 cals)
I'm hungry about the times that I eat.
I think the biggest deal is to just start eating about every 2.5 to 3 hours (force feed, if necessary) and try to keep your meal sizes about the same. Once your body gets used to it, you'll find it's not that big of a deal.