I'm in a debate with my water company about usage. Are there any methods to verify that the reading on my water meter outside my house is increasing at the proper rate?
Water meter calibration is something your water company can do for you, or you can hire an independent company to do it. I saw one water company charge $70 for calibration.
When water meters lose accuracy with age it is usually in your favor: large-scale calibration efforts have been profitable for water companies because replacing inaccurate meters usually leads to more revenues for them.
Before doing anything, test for leaks by turning off all faucets and appliances and verify that the meter stops. You can also learn a lot by watching the meter as you use water in different ways. (You will be surprised to see how much watering the lawn is costing you!)
You could try a rough DIY calibration by filling a large vessel of known volume, such as a kiddie pool, but you may need several samples to get an accurate estimate.
Here's what I'd do to verify your meter is working correctly. First, shut off the water to your house where it enters and note the reading on the meter. Give it a couple hours and check the meter again - it should be the exact reading it was before. If it is not, there is a leak between the meter and your shutoff.
Next, turn your houses main supply back on but don't use any water. Again, give it a couple hours and check the meter again. If it has changed then there is a leak somewhere in your house (or in the sprinkler system, etc.).
If you've ruled out leaks, now its time to use a fixed and measurable amount of water. Check the meter reading, then go fill a couple large bucks with a known size. Go back to the meter and check to see if it reflects the correct usage. If it does not then there might very well be an issue with the meter.
Also check that the reading the company is reporting is the same reading on your meter. If it is manually read, it could be a human error.