Well the best secret ever and always is the best tip I can give you all.
ALWAYS shoot from above!
When i train photographers in the studio. I get them to do a shoot and I edit their shots and I can tell immediately from looking at the image the mistakes and the classic one is that they always shoot from below and shoot upwards. Now unless you are a supermodel and are creating a Vogue front cover then this is not going to work with the average person.
Doing this will always always give the person a fat chin, neck and fat everything unless they are super skinny!
I am always conscious of this and its not such a bad thing as pictures are always memories! You will hide any double chin or any imperfections of the neck! It in fact makes you stretch the neck out so giving the impression it is longer than it is and also with gravity makes your wrinkles push back and stretches the skin on the face making you look younger! TRY IT, it really works!