If the tree is deciduous and has lost its leaves, you should be able to identify it by examining its buds.This is the most reliable way of identifying a deciduous tree in  winter. You will have to look at the buds at the end of the shoot and those along the shoot. 

Identification by buds can be difficult, particularly if the they are very small and not easy to see. So you may have to rely on other features in winter. Examine the bark, old leaves, old fruit, thorns, catkins or the tree shape and use one of the other options to see if they give you a clue to the tree identity and then check the buds again.

Opposite buds of Horse Chestnut


Horse Chestnut, Maples, Ash

Alternate spiral buds of Goat Willow


Willows, Poplars, Beech, Hazel, Birch, Alder

Alternate buds of Small-leaved Lime


Elms, Limes, Mulberries

Clustered buds of English Oak


Cherries, Oaks