I have to endorse what Cugila posted, testing post-meal is an absolute must to get an idea of what the foods are doing to your blood glucose.
The response to carbohydrates varies enormously and it seems to be fairly individual with some foods spiking for some people more than others. I've just done a detailed set of tests for a fortnight and discovered all kinds of things that caused my BG to spike, and by controlling that, I've kept my levels right down.
But perhaps the most important part is that it puts you in control. Once you know what causes the spikes, you don't need to have them. I was originally told to test first thing in the morning and last thing at night, which frankly doesn't tell you much about what is happening. So over the last fortnight I've tested before, one hour after and two hours after a meal. That gives you excellent information.
Even the HbA1c test only gives a picture of the glucose that binds to your haemoglobin and that's really an average particularly over the last few weeks to a month or so. You can't bring down the average unless you know what causes the peaks and it's the peaks that largely cause the secondary complications.
I think once you've got the results of post-meal testing, you are so much more in control and it ought to be the very first thing diabetics are encouraged to do.