Basically, for manipulating your circadian rhythm, light therapy is recommended as the first line of treatment (possibly supplemented with low-dose melatonin). The timing and intensity of light relative to when your internal clock thinks it is in the day determines the amount of slowing or lengthening of your cycle. So bright light during when your body thinks it is 'morning' will slow down the cycle, and bright light at 'night' will lengthen it. That's why many people use f.lux. But how much, how long?
Your cycle's natural free-running cycle length (without zeitgebers, or cues, to entrain it) appears to be determined by genetic factors. This is hard to measure without doing some tracking and, ideally, actually free-running. Pretty inconvenient.
This paper, which I look forward to reading in-depth, claims to have figured out optimal ways [took another look: general principles] of calculating the correct exposure and absence of light to allow for rapid recovery from jet lag. If true, it will probably make all light therapy much easier to do and calculate.