Begin by considering the structural components of your garden. The trees and hedges should be native if possible- although other species can be good for wildlife.
Native trees in the U.K. include:- Alder, Ash, Aspen, Birch, Bird cherry & Wild cherry, Crab-apple, Field maple, Hazel, Holly, Juniper, Oak, Scot’s pine, Rowan, Yew, Whitebeam, Willow and Wych Elm.
Native hedges to choose from include:- Hawthorn, Blackthorn, Wild rose, Holly, Hazel and Elder. Also, some native shrubs to consider:- Alder buckthorn, Blackthorn, Broom, Buckthorn, Dog-rose, Dogwood, Elder, Guelder-rose, Hawthorn and Spindle.
Then consider the situation of a log pile, in the shade, if at all possible. These will feed beetles and provide shelter for many other animals including frogs and toads. Hedgehogs also use log piles for hibernation.
Fallen logs make great retaining walls for flowerbeds. And logs cut to size make great wooden stools and tables.
Think about the direction of the sun in your garden throughout the summer and winter to make the best use of sunny and shady areas. If your garden is small this is not a barrier to wildlife gardening, make use of walls, roofs, and other structures to add to your space.