Here are some tips to capture those awesome colors the way you remember them: 1) Overcast skies are perfect conditions. The clouds serve as a natural diffuser which makes the colors pop out! 2) On a gray day with dull skies, minimize the amount of sky in your photo 3) Don't just settle for that stunning broad view of the trees, close in and take a few shots on the ground. 4) Depending on where you live, look for what I call the surrealistic juxtaposition of two or three seasons in the same photo! If you really want to get sharp, clear photos, use a tripod or place your camera on a solid object like a fence, car hood, rock, etc.
Here are just a few (low-res) autumn images which I have in my broad collection.