Rituals. I tried to repeat quiet time rituals when my son was a toddler. This included using voices in a quiet whisper, turning on classical music with sounds of the ocean, turning down the lights in his room. It was best to start this when I knew he would fall asleep shortly and then, when I needed it for a those times he had a difficult time settling down, I could start playing the music and whispering and it became a bit soothing.
He is a teenager now and finds it comforting to wear those old padded headphones and listen to music when he is studying.
I think I started pre-warning him of things that I thought would irritate him. I would say "oh, it's going to flash" or "here comes the noisy band" and this seemed to help him prepare to cope.
