A wiser writer than I distilled his writing advice down to these six questions everyone should ask themselves when writing.
Nothing I could add could make it a more effective.
What every writer should be thinking while they are writing by George Orwell:
1 What am I trying to say?
2 Which word will express it?
3 What image or idiom will make it clearer?
4 Is the image fresh enough to have an effect?
5 Could I have written it more succinctly?
6 Have I said anything that is avoidably ugly?
My favourite rule is number six. Is something I have written avoidably ugly? If it is unavoidably ugly I think I'd write it again.