Billions of garden birds die each year flying into windows, due to being confused from seeing foliage reflections in glass. Do not face indoor foliage to gardens (also make your garden safe for pets).
Lights Out Campaign says to turn off exterior/interior lights when possible, use window coverings and task lights and install automatic sensors, when you have no choice but to light certain areas. BirdSafe reviews best inventions to stop bird strike and also offers consulting and a volunteer manual to start a community FLAP program.
Those decals that you stick on windows are actually not that effective, unless you totally cover the window with them. More effective is bird-friendly glass which is still transparent to us, but has less reflectivity and etches patterns into the glass (the closer to each other, the better) so birds see a solid barrier, rather than clear glass.
The Bird-Friendly City is an American book, packed with ideas that work, from stopping light pollution and bird strike, to helping ground-feeding sparrows not fall prey to feral cats. The author takes us on a global tour of cities that are reinventing the status quo, with birds in mind. From innovative building designs to making urban environments bird-friendly (whether for migration or temporary shelter).
what to do if a bird hits a window
Some birds do recover if they are temporarily stunned but others may suffer internal/external injuries and die later on. FLAP has extensive info on what to do. Do not handle birds bird unnecessarily, nor give food or water. If birds need help, call your local wildlife rescue or vet.