The book made it sound easy. For each type of tree, two characteristics of the twigs are given, and that's enough to identify the type of tree (the book identifies them by genus, not species). I knew from my experience with summer identification that it's never as easy as it sounds. I also had noticed that the book did not include all the kinds of trees that I know are in my neighborhood. Thus to make things easy, I started off my examining some trees I already knew from my summer identification.
First I looked at ash trees. I could not see the twigs very well because the branches were too high. I had binoculars (a Christmas gift from my brother and his wife) so I used those to get a look at the twigs. I did see that they had opposite side buds and end buds. The book says that the way to tell ash and maple apart in winter is by their end buds, but either I couldn't get a good look at the end bud, or else I just didn't know what to look for, since I did not recall at that time what the book said about telling ash apart from maple. Also, in a residential neighborhood, I was a little uncomfortable about using the binoculars too much, for fear someone would think I was spying on them.
Next I looked at Norway maple twigs. This was easier because the tree was on a hill. By standing in a spot that was higher than where the trunk of the tree was, I could reach the twigs and get a good look. I saw that the buds were red. The side buds were opposite, and seemed to be in the same locations as the leaf scars. It seemed that the farther back on the twig I looked, the smaller the side buds got. The end buds looked like a cluster of a lot of buds. The twigs seemed to branch oppositely, but the big main branches of the tree were not opposite.
I got two pictures of the Norway maple twigs, but you can't really see that much:
After studying this tree for a while, I moved on. Walking down a street, I saw a tree and wondered what it was. I knew that it was a tree that I had identified in the summer, but I couldn't recall what it was. I examined the twigs, and found that the buds were opposite. From my summer identification, I knew the only opposite trees on this street were maples, so I knew it was a maple.
Farther down the street was a tree which I had not definitively identified in the summer. I thought I recalled that it had simple, unlobed leaves and perhaps some fruit. I took these photos:
The book says that the short, stubby twigs that can be seen in the top picture are called spurs and that they are found in apple and cherry trees. It also says that cherry trees have lenticels like birch, so I am thinking that this tree is a crabapple.
