That's my most common way of going lucid. Prior to a lucid dream, i might have a series of very long, very vivid dreams, wherein i actually notice things are out of place, but never do reality checks. One night, i'll notice a dreamsign, and just go lucid, just like that.
Regards melatonin, i've never taken it, i don't think you can get it here.
I still say the best thing for a good night's sleep and plenty of dreaming is routine, as far as is possible!