For children over the age of 2
I recommend the use of a sleep clock as part of my sleep program.
Your child's room should be blacked out, especially during the summer months - I love these cut-to-size instant blackout blinds.
Use a dim red/orange toned night light in your child's room. Avoid blue light which causes the body to suppress melatonin (the sleepy hormone).
White Noise Machines:
White noise can be helpful to reduce disturbance from siblings or external noises. The best kind is the fuzzy tv sound played constantly throughout the duration of sleep.