If you want to be certain of correct exposure, check the histogram and make sure you have the blinkies enabled (highlight alert, in the menu).
Regardless of what mode you're in or what the meter says, that will tell you what you've actually got, because it's taken off the sensor and is not an 'estimate' made by the meter before you take the picture.
In the very simplest terms, if the histogram is stacked to the right and the blinkies are flashing all over the place, and not just in naturally bright areas like sky or shiny reflections etc that you would often expect (and probably need) to be over-exposed, then you need to make adjustments.
Edit: if you want to learn about exposure, with digital, then Bryan Peterson's book is perhaps not the best way... :thumbsdown: