Being frugal can also be "green", almost as a side effect. The 4 Rs are a basic concept of being green, usually stated as "reduce, reuse, recycle, and rebuy," but I generally lump rebuy (buying recycled products) with recycle and make the 4th one "refuse," or don't buy at all. But frugal sages got there first with the very similar "use it up, wear it out, make it do, or do without."
Those are still good philosophies, and there are lots of ways to put any of them into practice, some of them familiar, some not. Some of these, I've mentioned before (Reuse) , but some I think are new:
What to do with ads papers? Many of these are printed in colored inks, and recyclers don't always take these. Even if they do, you can still get some extra use out of them before recycling. I keep a few around for frying foods, like bacon or hamburgers. I put down some colored papers, a layer or two of non-colored paper, then cover it with a paper towel. This is cheaper than using 3 or 4 paper towels for the same thing (and it's a good use for junk mail too). If you have a high-chair-aged toddler, you can spread layers of these on the floor around the chair and clean up by peeling off the top layer, also good for finger painting and other fun-but-messy crafts. And of course there are the better known uses, like lining a bird cage or under a paint drop cloth.
Plastic shopping bags can be recycled, but you can also reuse them a few times before recycling them. Keep a few in the car for grocery shopping. Keep a few in your briefcase or backpack for protecting books and papers if you get caught out in the rain. Use them to line small bathroom garbage bags. I put the canister for my vacuum inside a large shopping bag to open and empty it as well as to shake out the dust filter, keeping down the mess. They can be used as stuffing. Use them to dispose of particularly messy or smelly garbage. I've even seen them cut into strips and crocheted or woven into door mats.
Take a pair of jeans for instance, a treasure trove to my mind. Start with "use it up, wear it out" and wear them until they aren't wearable. If the knees or cuffs go out first, as they often do, cut them off to make shorts out of them and turn the useable fabric into shopping bags or patches for quilts (I think I described this in an early post.) If the body portion goes out, you can still usually get bags and quilt pieces out of them, and if enough of the body portion is useable, it can be turned into a bag as well. If not, you can get quilt squares and back pockets and zippers and the waist band and belt loops to use for other projects.
Old non-knit cotton (or linen or silk) shirts that have been worn out so far you can't patch or repair them can be cut up and the useable parts turned into quilt squares or shopping bags. And always save the buttons. Keep a jar with your sewing stuff just for buttons. Sleeves can be turned into funny purses or toys. One idea is to cut off a long sleeve, salvage any buttons from the cuffs, sew the cuff closed, stuff unusable scraps of fabric into the end until you have about a baseball-sized wad of soft stuffing, then tie a strip of fabric or ribbon just above the ball to hold it in place (a couple of stitches can help). Hem the upper end of the sleeve, then use it as a kind of sling toy to throw around (twirl it around, then throw to the other person who tries to catch it by the open sleeve to twirl and throw back).
Old knit shirts and shorts that are worn out can be cut up into cloths for cleaning (keep a few in your car, for instance). They can be cut down into shirt dresses for toddlers. Cut them into strips and braid them to make hair bands or belts or purse straps. I've even seen directions for making your own unique underwear out of old t-shirts, however my sewing skills are not adequate to test that. But it could be fun to try...
I've mentioned that I'm a full-time college student currently, and so is my youngest. Students invariably end up printing out stacks of draft papers and lecture notes, etc. I keep these, flip them over, and print the other side with anything that doesn't have to be submitted. I also cut sheets of used paper in half and staple a stack of these to make my own note pads. And once you've used both sides, the paper can get added to the stack of paper waiting to go under the paper towel to soak up grease or get recycled. Open up envelopes from junk mail and use them to make notes of something or for a shopping list.
Remember, it's all in the attitude.