ground rule

as a rule

In general; most often.

bright-line rule

A clear-cut rule, so that it is easy to make a decision.

common ground

A characteristic or interest shared by multiple people or systems; any belief, etc. held in common.

ear to the ground

The practice or characteristic of carefully gathering information; a state or mindset of attentiveness.

eyes on the ground

One or more observers in an area of interest.

facts on the ground

The situation in reality as opposed to in the abstract.

from the ground up

From the beginning; starting with the basics, foundation, or fundamentals.

get off the ground

To succeed or begin to succeed.