If you know where your main water supply is located, turn if off and check the meter. If it is still changing, you know the leak is between your house and outside meter. If there are none inside (and this might seem obvious), then it's likely coming from somewhere else close by - like at least one other faucet or pipe nearby!
A leak is sometimes very obvious; other times you could have a leak for months and not know it. There are a few things to look out for if you suspect a leak in your Atlanta area home:
Look at your water bill to see if your usage has gone up with no apparent reason.
Any musty smells could indicate a leak that has led to mold/mildew.
Any signs of wall, ceiling or floor damage, including stains, warping or bubbling.
Professional plumbers can do a thorough inspection of your home and grounds to determine if you have a water leak.