guidepost
guideline **
rule of thumb

The rule of thumb has been the more the better.

A good rule of thumb is that the higher the model number, the better.

This may not always hold true, but can be used as a rule of thumb.

Yet, there are a few rules of thumb to keep in mind.

As a rule of thumb, if you can see one from the other, it will work.

As a rule of thumb, the more you order, the lower the price per service.

The old rule of thumb had been no more than six months.

This is the rule of thumb for all new technology.

In the real world, the rule of thumb is you do what works.

There doesn't seem to be any general rule of thumb.