• Always be consistent in what you feed your cat in terms of protein, fat, carbohydrate, and fiber content of the diet, and when you feed your cat relative to the insulin dose.
  
  
• Make sure that the type of insulin matches how you feed your cat.  A shorter-acting insulin such as Vetsulin/Caninsulin often requires meal-feeding (or at least not feeding your cat after about 6 hours post-dose); longer-acting insulins such as PZI, Lantus, or Levemir may be more suitable for a cat who free-feeds.
  
  
• Consider the content of the diet. Cats on diets which are low in carbohydrates (around 5-10% of total calories) usually require less insulin than cats on high-carbohydrate diets.  In addition, a substantial minority (around 1/3) of cats who were previously on a high-carbohydrate diet may end up not needing insulin injections if carbohydrates are restricted.  There is now research indicating that Lantus (insulin glargine) may improve your cat's chances of being diet-controlled, especially if the dosing is aggressive.  Caution: a low-carbohydrate diet may not be appropriate for some cats with health conditions such as chronic renal failure or pancreatitis; check with your vet to see if this diet is appropriate.
  
  
• Once you become comfortable measuring your cat's blood glucose, it can be very helpful to keep track of how your cat's glucose levels respond to the food or foods that you feed him.  For example, if your cat experiences food spikes, this may affect your decisions about insulin dosage.
  

Regulation.  Regulation in cats is differently defined by different authorities, and the definition is evolving as the standard of treatment changes.  Here is one possible set of definitions (from the FDMB FAQ):

• Regulated: Blood glucose generally below 300 mg/dl (16.7 mmol/L) with glucose nadir near 100 (5.6), good clinical signs, no hypoglycemia
• Well regulated: Blood glucose generally below 200-250 (11.1-13.9) and often near 100 (5.6), no hypoglycemia
• Tightly regulated: Blood glucose generally below 150 (8.3) and usually in the 60-120 (3.3-6.7) range, no hypoglycemia, still receiving insulin
• Normalized: Blood glucose usually between 60-120 (3.3-6.7) except perhaps directly after meals -- usually not receiving insulin

Aggressive dosing.  Any dosing protocol which involves increasing the risk of hypoglycemia.  (Note: there may be good reasons for taking that risk, including avoiding diabetic ketoacidosis and other complications of chronic high glucose values.)

Tight regulation.  Keeping glucose as close to euglycemic (70-100 mg/dl or 4-5.6 mmol/L) as possible for as long as possible, and under 150-200 mg/dl (8.3-11.1 mmol/L) almost all of the time. This is a result, not a method in itself.   This is a desirable goal for the good health of the cat, and the main obstacle to achieving it is the risk of hypoglycemia.  A second obstacle is inconsistent response to a specific dose of insulin.

Tight regulation method. Any non-SLGS method which has, as its aim, to keep a cat tightly regulated.   (Note: the method may not succeed in its aim, and other methods might lead to tight regulation; the issue is the intent of the person using the method.)

TID or QID dosing. 

What it is:  Giving insulin three (TID) or four (QID) times a day, usually regularly spaced.
Purpose: To create a smoother glucose curve with less distance between the pre-shot value and the glucose nadir (low point).
Who might use it: Cats who have a wide range of blood glucose values even on a very gentle insulin.
Advantages: Keeps glucose levels more stable over the course of the day.
Disadvantages: Labor intensive, requires frequent testing, more restrictive to your schedule than BID dosing, more expensive due to increased use of syringes and test strips.

As-needed dosing. 

What it is: Giving insulin when the cat's blood glucose goes above a certain amount after the previous dose has peaked and the blood glucose is clearly increasing, typically somewhere between 150 and 200 mg/dl (8.3-11.1 mmol/L), without regard to the clock.
Purpose:  To keep glucose levels consistently in desirable ranges.
Who might use it: Cats who do not have a consistent response to insulin, and people who are attempting to achieve tight regulation with their cat.
Advantages:  When the cat cooperates, blood glucose levels are kept in or near euglycemic ranges.  A little more flexible than TID or QID dosing.
Disadvantages:  Requires frequent testing both to determine when the previous dose of insulin is past peak, and when the blood glucose rises enough to require a new dose.  May cause confusion if the previous dose did not lead to a clear glucose nadir.  Potentially expensive due to increased use of test strips.

Bolus (booster) dosing.

What it is:  Giving small doses of fast-acting insulin (Humulin R, 70/30, or N), as an adjunct to the usual dose of long-lasting insulin (PZI, Lantus, or Levemir).
Purpose:  To promote a rapid drop in blood glucose over a short period of time.
Who might use it:  Cats who tend to have food spikes;  cats who tend to have too-slow response to their long-lasting insulin; cats who occasionally don't seem to respond to their usual insulin; cats who are prone to adverse complications of high glucose, particularly ketones; cats who have a difficult time coming down from high numbers.
Advantages:  Helps handle high glucose values swiftly and usually predictably.
Disadvantages: Requires keeping extra insulin around, may require extra syringes; frequent testing needed; risk of hypoglycemia if too much is given; may inadvertently be used when the real solution to the problem is to increase the dose of the cat's usual insulin.  More expensive due to increased use of syringes and test strips.
Comment: Can be given with the regular shot, or between shots.  Can be given regularly or on an as-needed basis.  Dose can be varied according to blood glucose level.
Warning 1:  In some cats,  1 unit of a fast-acting insulin can quickly drop their blood glucose by hundreds of points in a short period of time.  It is crucial to start with miniscule doses and assess the action of the insulin by testing every hour until you have data on how much insulin you can safely give.  This is a very dangerous technique if not properly used.  Treat the fast-acting insulins with respect!
Warning 2:   If your cat has diabetic ketoacidosis, she belongs in the care of a vet.  DKA requires  making sure electrolyte levels are balanced before giving insulin.  Do not attempt to treat DKA at home.

Sliding scale dosing.

What it is: Basing the insulin dose on the pre-shot value -- less insulin if the pre-shot is lower, more insulin if the pre-shot is higher.
Purpose:  With usual insulin, to reduce the risk of hypoglycemia if the cat has an unusually low pre-shot glucose value.  With bolus doses, to handle unusually high pre-shot values.
Who might use it:  Any cat who has a low pre-shot number; users of the Dr. Hodgkins protocol; users of boosters (with the booster insulin).
Advantages:  Avoids hypoglycemia.
Disadvantages:  Reduced dose may lead to high pre-shot in next cycle for those dosing by the clock, or short duration for those using as-needed dosing. 
Comment:  Primary variations are: a.) having a standard dose for the cat, but giving less insulin if the pre-shot is unexpectedly low, and b.) varying the dose from one shot to the next as a general practice.  Use of sliding scales may not be necessary with very slow-onset insulins, but that should be determined with data from your own cat, assuming that a reduced dose is necessary unless you collect clear evidence that it is not.

Varying needle length

Comment:  Needles are typically available in 1/2-inch and 5/16-inch lengths.  For some cats, needle length has been shown to make a difference in onset and duration of insulin, possibly because the probability of inadvertently shooting into the fat layer is different.

Varying injection site

Comment:  Onset, action, and duration of insulin may be different if the injection is done at different sites.  If inconsistency is a problem, you can try experimenting with injections between the shoulderblades, between the thigh and the side of the body, or at the abdomen.  Do not inject into muscle: insulin injections must be subcutaneous.   Injecting at the scruff of the neck is thought to lead to inconsistent absorption.