Some other tips:

1. As with sleeping normally at home, avoid 'blue' light, so don't use screens such as watching in flight movies, phones, tablets, laptops. Reading a book is best.
2. Alcohol isn't really a solution for most people.
3. Altitude doesn't help sleep and neither does noise. Can't do much about the first (other than choose your aircraft wisely as some have a lower cabin altitude than others) but earplugs can be a Godsend.
4. Practice can be key. My wife (CC) found that when she started flying professionally she found it quite hard to sleep on her breaks, however it comes reasonably easily now. Presumably those people that fly LH frequently, find it easier to sleep, whereas if you don't do it that much then it's probably more difficult.