This is a great site with a lot of information as well as support from other members. It would be good if you could tell us about your cat (age, what led to diagnosis, other health issues) and especially what he eats. Have you started giving insulin? Type ? Dose?
Generally, there are 3 important things to managing diabetes in cats.
DIET: wet, lo carb food is best. Most of the pate types of food such as Fancy Feast, Friskies, Whiskas etc are good. Dry food is too high carb, even the so called prescription food. Wet food more closely mimics the natural diet of cats (mice are pretty high moisture content). Cats with urinary problems benefit from wet food too. For treats, freeze-dried chicken is the best. Most cats love it and come running at test time.
HOMETESTING: This is essential to know how food change and/or insulin is affecting your boy's blood glucose number. Most of us use human glucometers and test the ears. Cats soon get used to this procedure, especially if accompanied by lots of freeze-dried chicken treats.
INSULIN: I personally prefer the longer acting insulins like Lantus or Levemir, it depends a lot on where you are and what you vet will use. I suggest that you read the notes (stickies) in each of the insulin-specific forums on this site to get a good sense for how each works.
I know it is a steep learning curve, but in no time you will have a routine worked out that works for you and your boy.