TOMORROW MAY BE the first Earth Day since 1970 when a majority of Americans are actually aware it's happening. The eco-holiday went underground for decades and had a low-key relaunch in the 1990s, but this year, "green" is suddenly everywhere and more people than ever are taking a look at their carbon footprint.

It helps, of course, that our government is now pro-environment, bringing a more active Environment Protection Agency and promising to create a "green jobs" market. And that the data on human-caused climate change keeps getting stronger, which is bad news for humanity but good news for eco-marketers!

If you're one of those who hasn't been too eco-active before now, but are seeing Earth Day as the perfect time to jump on that hybrid-synergy-drive bandwagon, read on.

First you need to start talking green. See? Right there's an example. Green is no longer just a color - it's a noun, a verb, an all-purpose adjective and, why not, an adverb! Use the word liberally in whatever context needed to show all-encompassing "green" is. If you need something more specific, try adding "eco-" to the front of whatever term you would normally use, as I've illustrated above.

Once you've greened your tongue, next comes your wardrobe and personal accessories. Are your clothes organic, made from hemp, soy or bamboo? If not, throw 'em in the trash and don these trendy textiles, especially if they're in the form of a T-shirt that proclaims "Be the Change You Want to See!"

Then stock up on some "eco-chic" items from suddenly green outlets like Barnes & Noble, where you can find a purse made of old bottle caps, or the Disney Store, where on Earth Day you can bring plastic bottles for recycling and get back a reusable water bottle (while supplies last).

Be sure to grab a bunch of the newest, trendiest electronics, namely solar gadgets. From flashlights to cell-phone chargers to backpacks to digital keychains, everything now seems to be available in a solar-powered format, including, from EarthTech, the World's Smallest Solar-Powered Car!

Toss as well all those harsh-chemical-based cosmetics and household cleaning products and restock with those that feature beautiful pastel colors and pictures of the sun or flowers, or with labels like "natural" or "contains organic ingredients."

OK, wait - in all seriousness, some of those tips may be somewhat counterproductive.

Really, don't throw stuff in the trash if you don't absolutely have to. More generally, though, if you try going green by spending green, you quickly hit some cross-purpose speed bumps: What if an item is made from organic ingredients, fair trade produced, but in a wasteful nonrecyclable package? Is environmentally friendly bamboo from China still a good bargain for the planet? And might your renewable-energy purchase cause trouble for wildlife populations? Who has the definitive answers?

It gets worse: If you're relying on product manufacturers to guide you to greenhood, you may be surprised and appalled by the results of a study by TerraChoice, an environmental marketing firm. It found that the vast majority of items marketed and/or labeled as "green" had some misleading environmental claim. And by vast majority, they claim 98 percent.

Now, most of these "greenwashing" sins are not outright lies, but claims without verification or omitting to mention hidden trade-offs in the overall production of the item. But now that "green" is hot, more companies are slapping some variation of the word on just about anything, and relatively few are stopping to get credible third-party certification of their claims.

In short, though the marketplace is the most visible forum for Earth-friendly progress, there are more straightforward ways to change little things today that can add up to a much more sustainable lifestyle. (These are a small sample: You can get many more ideas from green media like Earth to Philly, or philly.com's Green page, or Treehugger.com.)

First off, check your household's output into the waste stream. Participating in the city's curbside recycling program is a no-brainer - at the very least you know you throw cans, bottles, cardboard and non-glossy paper in there. Once you've established that habit, you can move to checking plastic containers for #1 or #2.

And even if you don't have a back yard, you can compost your organic waste in a small aerated container under your sink, especially if you add bedding such as shredded newspaper and red worms that will process smelly garbage into odor-free compost you can give to grateful gardener friends.

Check your input, too, though: Are you bringing extra crap into your house out of habit? Do you get a plastic bag for two items at the convenience store even though you could carry each in one hand? Do you buy a certain product in a small size every week when you could get a larger size that would last as long but would only generate one piece of trash? Can you find ways to decrease the total amount of trash you set out on the curb by, say, one-third?

If you drive, it's not necessarily a question of switching entirely to SEPTA/PATCO (though if you think about each trip, you'll likely find some where walking/riding would be just as doable) or buying a new hybrid car. While those come with a display to show you your gas mileage moment-to-moment, you can still change your driving pattern and maximize mileage in the car you have.

Some simple principles are to avoid braking (i.e. don't drive faster than you need), embrace coasting and start smoothly from a stop at a light. And yeah, it's been said a million times, but having your tires properly inflated will improve your mileage.

Also, since your car engine works more efficiently when warmed up, if you have multiple quick errands, drive to the farthest one first, so you give the engine time to warm up for the trip back, instead of the other way around, where it might not get warm till you're practically home again.

The key change to make in driving green is to lose the conviction that there's some award awaiting you if you finish the course in the shortest possible time. I know, this is a hard one for Philadelphians, but it can be done!

And here's another little step that can mean a lot: Batteries. Everybody uses some batteries sometime. Once used up, they're little toxic bundles of woe for the planet. We used to just toss them in the trash, i.e. landfill, i.e. into the earth. And it was hard to find a place to drop them off for recycling. But Whole Foods on Callowhill Street, for instance, has installed a dropoff container. Just remember to take them with you - which reminds me . . .

A key tip that's making the rounds of both green sites and save-money blogs is to stop and think every time you buy something for less than $5. As often as not, it may be something you could do without.

There are exceptions, though (of course the biggest is the Daily News. Don't deprive yourself of that!). If you're at the grocery and they have those reusable bags for sale for a buck or two, it's probably worth it to buy more than one.

Why? Because if you're like me and everyone I've ever talked to, you will bring your food home in one and forget to put it back in the car for next time - thus winding up bringing home more paper or plastic. Having at least two on hand lessens the odds of winding up in the checkout line and realizing your eco-bag is at home.

While we're talking groceries, one often-overlooked tip - and one that makes an impact multiple times a day - is to modify your consumption of livestock-based foods (meat and milk, mostly). Livestock produces more greenhouse gases than all of human transport, so sticking to plant foods for even a few meals a week can make a big difference (at least compared to, say, turning off the water while brushing your teeth).

Earth Day could be a good excuse to try a day without animal products. A recent Huffington Post piece noted that if every American went vegetarian for just one day, we would save 3 million acres of land, 33 tons of antibiotics, and 70 million gallons of gas - "enough to fuel all the cars of Canada and Mexico combined, with plenty to spare."

So it could be that the greenest products aren't even products. In other words, maybe Earth Day doesn't come from a store. Perhaps, just perhaps, it means a little bit more - or rather, less.

Westerners like us are used to living large, taking a big bite out of life and throwing away the proverbial peel as cogs in some consumerist contraption. But face it: That's something we can, and must, start changing now. We needn't live monastically, but a better option than a new purse made out of old bottle tops or a hemp baseball cap might just be . . . not buying a new purse or cap.

So out of all the celebrations, festivals, and high-profile spectacles, what's the perfect Earth Day activity? When all is said and done, it might just be stopping everything you're doing and going for a walk. If you find roses to stop and smell on the way, so much the better. *