I've always loved trees. Years ago a friend and I would take woods walks and started a little contest to see who could ID different trees. After both of us got good at IDing most of the trees in the area(this was coastal SC) we changed the rules so you could only look at the bottom 4' of the tree. That put a wrinkle in how well we could ID trees but it tought both of us some good, useful info.
Twig and buds are probably the best ID next to flowers. The structure of a tree is also a very good ID method as are leaves. Once you learn a few of these methods and utilize them tree ID becomes a lot easier. If you are a selfbow builder, knowing trees and their characteristics will serve you well in your bow building.
A good tree ID book like the Audubon Field Guides(and others) are a great resource and are made to carry with you in the field.
I'm not a taxonomist or a dendrologist but I love trees so IDing them is fun for me. Like riding a bike, once you learn it is isn't hard to remember most of the info.
Yep, leaves are only on 6mo out of the year, only leaves bark and twigs to ID by after that. Structure is a good one too, but woods grown and open grown are totally different. Shade tolerance and moisture tolerance are two subtle clues to help determine.
Once you learn all the different tree species, you can catalog different characteristics....deeply furrowed bark...hmmm sourwood, black locust, large honey locust, large walnut, chestnut oak....then you can narrow it down again with other characteristics.
First thing I look at when I can is venation. If it's alternate then it could be a variety of things....if it's opposite it's a MAD Cap Horse....Maple Ash Dogwood...Caprifoliaceae (viburnums)...horsechestnut (buck eye)