Question:
Should hands be joined at chest height or at waist height?  How should dancers move in to meet at the start of the formation, do they curve in or dance diagonally down?

Answer:

Hand height depends very much on the respective heights of partners.  Generalising on waist height leads to hands too low, while generalising on chest height leads to hands too high !   The optimum is somewhere in between. We seldom have partners whose waist is at the same height as our own but leading nearer waist than chest height is preferable here.  The Manual has it right saying "about waist height" (para 6.17.1)

Traditionally the entry has been taught by dancing diagonally down to meet your partner on bar 1

Often dancers go straight in to meet partners but that spoils the flow of "down the middle". 

Curving in-and-down may be felt to be more sociable, but a diagonal start gives more flight.