I found an interesting article on sexing chicks. Not sure if it is accurate, but it is informative.
http://www.backyardpoultrymag.com/6-3/determining_sex_in_chicks/
Vent and wing sexing is what hatcheries use (some use one some use the other), it tends to be pretty accurate once you get some experience. Nome of the other methods are true in my experience, not the egg, temps, or dangling from head. Then the obvious wait and watch method. There are some really good videos on vent and wing sexing. I know how to do both, but wing sexing only works on offspring bred for the fast and slow feathering and I prefer not to vent sex.