Grice, discussing conversation but implying a wider applicability, suggests just such a 'rough general principle which participants will be expected (ceteris paribus) to observe' the Cooperative Principle:

Make your conversational contribution such as is required, at the stage at which it occurs, by the accepted purpose of direction of the talk exchange in which you are engaged.

He goes on to distinguish four categories from which he derives a number of specific maxims:

Quantity

1. Make your contribution as informative as is required (for the current purposes of the exchange).

2. Do not make your contribution more informative than is required.

Quality

1. Do not say what you believe to be false.

2. Do not say that for which you lack adequate evidence.

Relation

1. Be relevant.

Manner

1. Avoid obscurity of expression.

2. Avoid ambiguity.

3. Be brief (avoid unnecessary prolixity).

4. Be orderly.

An interesting suggestion, which connects well with translation, has been made; that these conventions are close equivalents to the constraints which operate in intra- and inter-lingual code-switching, i.e.