Start a garden journal, using notes and photos. It will help you notice what's going on in the garden and give you a wonderful record to look back on.
Pile up chunky dead wood as a shelter for mini-beasts and their larvae. If you can, part-bury some of the pieces, as a few species prefer this.

Check your structures - that is, plant shapes and sizes! Variety matters; and trees, shrubs, climbers, perennials and annuals all contribute to a wildlife garden.