While it is important to know all the different insulins and times of action, peaks, etc, you should also listen to the pt. Many of the pts who will need insulin will have been taking insulin for a long time and will know their own body. Some people have huge drops in blood sugar at night, and so will not want to take insulin at night. For example, I had a pt the other day who had a blood sugar of 152, and according to her SSI, she was to get 4 units of regular. She didn't want to take it because sometimes her sugar goes into the 40s over night. I didn't argue with her, and sure enough, even without the insulin, she was 64 in the am. Had I given her the insulin, she may have dropped way lower and had problems. It doesn't feel good to have your sugar too low! Then some people are more sensitive to insulin than others are, so moral of the story, if your pt is lucid, allow them input into their care!
Of course, if her sugar had been 400, I would have argued a bit more about letting me give her the insulin!!!
You should find a chart you like and carry it with you. I'll look around for mine and post it later if I can find it.