Any tricks for getting "contractor" discount on supplies?

My wife and I just spent the last two years building our own home. We
didn't even try getting "contractor" discounts on our building supplies.

Despite that, we often received contractor pricing on many of our larger
orders anyway because of the size of our purchases.

Also, we purchased many items at home centers (Lowes, Home Depot, etc.)
cheaper than some contractors prices.

In addition, we ordered many supplies (faucets, timers, special plumbing
and electrical supplies, etc.) on the internet and saved a bundle over
local pricing.

Anthony