well, obviously no one can ever be certain when the leaves will change. But Yankee Magazine provides a predictor map, which will give you a general idea.

http://www.yankeefoliage.com/peak-foliage-forecast-map/

Pick the first or second week in October. First week will probably be best for northern New England. Second week for central and southern. Quite a few towns have a Columbus Day weekend event so you might want to choose one as a destination. Keep in mind that different varieties of trees changes at different times plus the same variety will color sooner at colder, higher elevations and latitudes. There is no best weekend. It's a beautiful production over several weeks. The most colorful are the sugar maples because they can be orange and yellow and a little green all at the same time.

You can't go wrong with leaves Columbus Day weekend. You may have snow at the higher elevations, which is beautiful.

Find your hotel soon. Prime areas go fast because it is a public holiday for New Englanders as well as a peak time for tourists.

The only thing that might go wrong is rain, but that usually is not a big deal until later in the month.

And Vermont and New Hampshire are Tweedledum and Tweedledee. Both states are so small that you can drive over into the other one (or into Maine) if you feel like you are missing something.