We've all probably been guilty of this recycling no-no at least once — discarding a disposable coffee cup or food takeout container in our bin. While you may be thinking you're doing your part to help, your optimistic recycling may actually be hurting the process.
Depending on where you live, there are some items that simply aren't recyclable, including varieties of paper, glass and plastic. Check with your city service provider to know specifics, but here's a list of items that generally are not recyclable, along with suggestions on how you can dispose or reuse them.
Aerosol cans: Sure, they're metal. But since spray cans also contain propellants and chemicals, most municipal systems treat them as hazardous material.
Batteries: These are generally handled separately from both regular trash and curbside recycling.
Brightly dyed paper: Strong paper dyes work just like that red sock in your white laundry.
Ceramics and pottery: This includes things such as coffee mugs. You may be able to use these in the garden.
Diapers: It is not commercially feasible to reclaim the paper and plastic in disposable diapers.
Hazardous waste: This includes household chemicals, motor oil, antifreeze and other liquid coolants. Motor oil is recyclable, but it is usually handled separately from household items. Find out how your community handles hazardous materials before you need those services.
Incandescent light bulbsStandard incandescent bulbs can't be recycled, but the more energy-efficient CFLs are. (Photo: Justin Sullivan/Getty Images)
Household glass: Window panes, mirrors, light bulbs and tableware are impractical to recycle. Bottles and jars are usually fine. Compact fluorescent lightbulbs (CFLs) are recyclable, but contain a small amount of mercury and shouldn't be treated as common household bulbs. For ideas on how to handle them, see 5 ways to dispose of old CFLs.
Juice boxes and other coated cardboard drink containers: Some manufacturers have begun producing recyclable containers. These will be specially marked. The rest are not suitable for reprocessing including many disposable coffee cups from your local coffee shop.
Medical waste: Syringes, tubing, scalpels and other biohazards should be disposed as such.
Napkins and paper towels: Discouraged because of what they may have absorbed. Consider composting.
Paper towels: Tissues and napkins are also included because they typically hold too much residue.
Pizza boxes: Too much grease. While some compost enthusiasts steer clear of adding pizza box cardboard to their pile, others report no problems. It's that or the trash.
A woman in Monterey Park, California, carries her groceries in a plastic bagPlastic bags may be convenient for us, but they're not terribly convenient for the environment. (Photo: Frederic J. Brown/AFP/Getty Images)
Plastic bags and plastic wrap: If possible, clean and reuse the bags. You can even return them (along with many other plastic film products) to your grocery store or through RecycleBank.
Plastic-coated boxes, plastic food boxes, or plastic without recycling marks: Dispose of safely.
Plastic screw-on tops: Dispose separately from recyclable plastic bottles. Remember that smaller caps are a choking hazard.
Shredded paper: While most plain paper can be recycled, it's hard for recycling centers to determine the type of paper if it's shredded. However, you can use the shredded, plain paper in your compost or mulch.
Styrofoam: See if your community has a special facility for this.
salad in plastic boxPlastic takeout containers technically can be recycled if done in the right way. (Photo: Patcharida/Shutterstock)
Takeout containers: Plastic containers that contained food can't be recycled unless they are thoroughly rinsed out. Oily residue left on the containers makes them unrecyclable.
Tires: Many states require separate disposal of tires (and collect a fee at the point of sale for that purpose).
Tyvek shipping envelopes: These are the kind used by the post office and overnight delivery companies.
Wet paper: In general, recyclers take a pass on paper items that have been exposed to water. The fibers may be damaged, and there are contamination risks.
Wire hangers: Most centers don't have the capability to recycle wire. However, most dry cleaners will gladly take them off your hands.
Yogurt cups: Many centers don't recycle plastics with the numbers three through seven. These items are typically food containers such as yogurt cups, butter tubs, and oil bottles. 
Your municipal recycling system gets the final say as to what belongs in your bin. Some areas will restrict more items that we've listed. Other have special programs for dealing with problematic materials. In most cases, municipal systems are happy to provide written guidelines. Wondering how to recycle something your local system won’t take? Pop over to the Earth911 website and see what is available in your area.