Read a boring book in low light while lying down until you pass out from boredom.
0.3mg (300mcg) of melatonin (you can buy capsules in this low dose)
500mg-1000mg of L-tryptophan
100mg L-theanine
The last two are amino acids. The melatonin is a very low dose. People usually take overdose of melatonin which causes the tolerance buildup.
L-Tryptophan converts into 5-HTP and then into serotonin and into melatonin in the body. This is the natural pathway.
L-tryptophan -> 5-HTP (5-hydroxytryptophan) -> serotonin 5-HT (5-Hydroxytryptamine) -> melatonin (N-acetyl-5-methoxytryptamine)
The l-theanine is found in green tea, which is what make green tea relaxing.
I think it is best to take on an empty stomach so that these amino acids do not have to compete with other amino acids in food to cross the blood-brain barrier.
I would only take if really necessary, ie if you don't need to be up in the morning it doesn't really matter what time you go to sleep.