This is one of those questions where you can ask 10 people and get 10 different answers.
My own view is that it rather depends on how much control you want to have over your condition. Many people have found that they can delay the onset of diabetes, often for many years, by a simple reduction in the carbohydrates in their diet. If you intend to reduce your carb intake (not necessarily a low carb diet, just a small reduction) then you will want to see what the result of that reduction is, so you will need to test in order to see what is happening. The ideal would be to test before each meal (preprandial), then at 1 hour after eating (postprandial) and again at 2 hours after eating. Before you eat your blood sugar level will be at its lowest point, at food+1 hour it should be near its highest, and at food+2 hours it should have reduced to somewhere near the before-meal level.
If that sounds a bit over the top and you only want to test once a day, or once every few days, then make sure that your test is always done at the same time, for example first thing in the morning when you get up. If you test at different times on different days then you're not comparing like with like so you won't be able to see any pattern emerging.