Make sure there are plenty of bushes and trees and as wide a variety of plants and flowers as possible to attract insects they can feed on. Sources of fruit like grape vines and strawberry patches will also attact birds if you don't mind losing your crop. I had grapes growing back in Cardiff in Wales and very autumn as soon as they were ripe blackbirds and flocks of starlings would fly in and tuck in!
Bushes and thick hedges are good for encouraging birds to nest in your garden.
A bird-table is a good idea so cats cannot get to them. Peanuts and coconut hung up will attract tits.
A bird bath is another attraction for birds.
Many common birds will soon learn where they are being fed and you can buy birdfood seed mixes specially made up as a supplement for bread and other human food scraps.
Finally if you have wooden fences, trees or other suitable places to fix nest-boxes this is something else worth trying. But remember to put the nest-boxes out of the range of cats.