i'm not an admin, but based on personal experience, it would depend on your body's response to the insulin, and the lifestyle you have. usually you'll be given 1 short-acting (like Actrapid) and 1 long-acting (like Lantus) insulin type. rapid-acting insulin can start between 5-30mins and work between 2-6hrs, at different peak times. long-acting insulin can work, i think, between 8-20hrs, with its effects spread out more evenly so that you avoid reaching blood glucose level peaks. your doctor will also give you a schedule that should work around your lifestyle, esp meal times and glucose peaks (example, if you usually get peaks after lunch, you might get a shot of rapid-acting insulin before lunch, etc.)
do consult with a doctor. treatments are best personalized
The best insulin combination depends entirely on your body, your diabetes and your lifestyle.
Many people take a basal-bolus combination as @slaxx has described.
Others take a mixed insulin.
And, if you are on a pump, it is different again.
Only you and your doctors can work out what is best for you.