There’s this principle I follow, for writing dialogues… It’s not really evolutionary or anything and there are chances that you might already be doing it, but then hey– no one reads my blog. So, I have no responsibility to serve only useful stuff.
Well, the trick is to try and write your dialogues in such a way, that it becomes easy for the actor to enact them. In other words, dialogues need to invoke emotion in the way they are read. The best way would be to act out the scenes yourself in your head and then write.
You see, The test for a screenwriter lies in invoking emotion out of an otherwise bad actor.
And, the test for the actor lies in invoking emotion in bad dialogue. (Amitabh bachchan does it really well.)