Listening to speech

I often find that a good way of developing dialogue is too compare real life situations with their 'dramatic' counterparts.

People do not actually talk in the same way as characters in plays, TV drama or films.  Real speech is different.

I get ideas for characters from such situations as overhearing fellow passengers on a bus journey or in people in a bar. Converting these moments into useful snippets of fiction is another matter.

I find that listening to the sound of well written TV Drama is often instructive. I do not watch the pictures but just study the interaction of the characters.  

But the best way to write good dialogue is to practise!