That’s the advice from a beautifully-executed campaign from Denver Water , right here in my own backyard of Colorado. The campaign (created by Sukle Advertising + Design , a very smart, strategic ad agency) is simple and effective, using guerrilla marketing to hammer the message home. But it’s not just good advice for water; I think it’s a strong message for all consumers.

It was a moment of clarity for me when I was picking up a Red Box DVD at my local McDonald’s and saw a guy grab maybe 20 napkins and shove them into his take-out bag. I had seen the Denver Water billboard earlier that day, and the two just slammed together in my head. “Use only what you need!” I was shouting at him in my head. Of course, if I’d said that out loud I would have risked spending a few nights in traction, so I did what most of us do…I kept quiet.

20 napkins to eat a cheeseburger and fries? Did this guy have a serious eating disorder that caused him to spill most of the food from his mouth? I can’t imagine why anyone would need more than a couple of napkins (parents of young children excepted, I know what kind of a mess they can make).

So, I started looking around the rest of the fast-food eatery. People were grabbing handfuls of ketchup packets, using two or three and throwing the rest in the trash. Sodas were refilled to the top, and thrown away half full. This was all just from one McD’s.

Over the next few weeks, I saw the wasteful nature of our society everywhere I looked. In bathrooms guys were grabbing six or seven paper towels to dry their hands. At a local buffet I saw mountains of food left on plates. It was all thrown away. Ironically, a sign near the buffet said “take all that you want but not more than you need.” I guess people ignored the second half of that message. And peering into garbage cans on the street, I was amazed at how much half-eaten food was thrown into the trash.

I have a bucket of Halloween candy on my desk that could feed a small army. I always buy too much, every single year. Will I ever learn? A lot of it will go off before it’s eaten. That also goes for bulk-buying at the warehouse stores. Buy only what you need, you don’t want to have a mountain of buns or granola bars if half of them go stale before you can eat them.

As I trawled through Craigslist, I saw people giving away all sorts of stuff they had bought too much of, including household paint and driveway gravel. (At least other people were getting use out of this stuff though, which is great. Recycling rules.)

I’m guilty, too. At work, we throw away reams and reams of paper each day due to mistakes, or more often than that, printouts for 10 people that are thrown away after a 30-minute meeting. In this day and age of electronic everything, we really need to be thinking about more efficient, and less wasteful, ways to conduct our daily business.

At home, I also found myself being wasteful without even realizing it. Take something simple, like Mac ’N’ Cheese. I made a box for my girls knowing that they would both leave some at the end of the meal. It was laziness on my part. And that’s no excuse at all.

A phrase like “use only what you need” should be good advice for all of us, ingrained from a small age until the day we die. If we all follow that advice, think of the savings we’d make as a society; savings that could be passed on to us, the customer. So give a thought to anything and everything you consume over the next few weeks, from a simple printout at work to a whole meal for your family. Use only what you need; take only what you need; buy only what you need. Nothing more.