Make your contribution as informative as is required, but not more, or less, than is required.
The Quantity maxim
Do not say that which you believe to be false or for which you lack adequate evidence.
The Quality maxim
Be relevant.
The Relation maxim
Be clear, brief and orderly.
The Manner maxim
To show that we are not really sure that what we are saying is really correct or complete.
To indicate that we are observing the maxims.
Hedges