To me the first tip is don't panic about not sleeping. The more worried one is about it, the one less sleeps. I disagree with the tips on booze, it makes you less likely to sleep and worsens the sleep quality too. Try to enjoy your flight, eat and drink likely apart from water (no problem at all about enjoying a glass or two of something but I wouldn't go beyond that), enjoy a book or a film, and when you start feeling tired try to sleep. In Y, I never manage (unless I have an empty row so can lie down) but in J, it usually works for me like that.