Most jurisdictions have specialists, usually R.N.'s or nurse practicioners that are very good at this. To do so yourself you have to eat consistent meals, of approximately the same number of calories. If you eat in a senior center the number of calories are about the same every day.
Then you have to start a period of intense testing with blood sticks.
That means when you get up. Before a meal, and two hours after a meal.
A lot depends on the diabetic medications you are on.
There are different kinds of insulin and each requires a slightly different procedure.
They key is to eat exactly the same meal when you experiment. If you have two scrambled eggs on a roll with a squirt of catsup and a slice of cheese, plus a coffee with a dab of milk and a sweet and low, once you determine what is required to give you an acceptable glucose level two hours later you can do the same thing whenever you have that exact meal.
A good diabetic nurse will assist you in planning means and making up such a chart. With the new meters the glucose levels are recorded, but exactly what you eat is not. For a while you need to keep meticulous records of your food intake.The best way is to come up with some "standard" meals. Standard breakfasts. Standard Lunchs. Standard dinners. There are diabetic cookbooks and dieticions that are extremely helpful in this respect.
I think you need to contact, as waverider suggested, a professional to assist you in this process.
Not everyone is the same. Discuss YOUR scale with your treating doctor.