Number one, far and away, is arranging my schedule such that I don't have to set an alarm clock. I did this once in college when I was able to get only late classes, and I do it now since I work for myself (although the kids sometimes wake me up). Any time I can go for a week or more without setting any alarm clock, I feel far more refreshed throughout the day.
Number two, no blue light at night. I went a little nuts with this one, not only getting flux, but I work in the dark at night with the brightness on the monitor at the lowest setting with a blue filter, and I also replaced all the night lights in my house with special night lights that run at 1850K (candlelight). I also installed a second light in bathroom with it's own switch and installed an 1850K LED bulb in it so that I could do my nighttime routine in "candlelight". Basically, after the kids are down, there is no source of blue light anywhere in my house.
These two things seem to have made the most difference. I've done other experiments with temperature control, sleeping position, bedroom darkness, etc. They all seem to make some difference as well, but not nearly as much as those first two things.