When to use ‘besides’, ‘except’ and ‘apart from’

The words besides, except and apart from are sometimes confused. Here’s a note on how to use each of these properly:

‘besides’ usually adds; it is like saying ‘with’ or ‘plus.’
Example:
Besides English and French, he can also speak Spanish. [He speaks three languages]

‘except’ substracts; it is like saying ‘without’ or ‘minus.’
Example:
I have watched all of Bruce Lee’s movies, except ‘The Big Boss.’

‘apart from’ can be used in both senses.
Example:
Apart from English, he speaks French and Spanish.
I have watched all of Bruce Lee’s movies apart from ‘The Big Boss.’

After ‘no’, ‘nobody’, ‘nothing’ or similar negative words, the three expressions can all have the same meaning.
Example:
He has no one except/besides/apart from his mother.