Meat, Grease, Bones, Skin
Never put these in your bin unless you are determined to attract rodents, scavengers, maggots, flies, terrible odors, bill collectors or even a snooping health department official.
Branches & Wood Chunks
Such material is best chipped up for paths or mulch. Even if shredded, they have a very high carbon content for a compost bin.
Large Amounts of Soggy Materials
Sloshy, matted, soggy, water-logged (you name it!), these materials (such as garden debris, fruit wastes, etc.) will turn your bin into a swamp. Best to let them air out and dry out, then you can put them in the bin.
Wood ashes, Lime, Charcoal
Some people use wood ashes or add lime to their compost bin. We don't recommend this because they are too alkaline and would raise your pile's ideal pH level of 6.8-7.0. Many plants (blueberries, strawberries, azaleas, natives, etc.) wouldn't like the results either. Never compost BBQ ashes or coal: the sulfur dioxides and other chemicals will give the little worms and plants in your garden bad stomachaches.
Solid wastes: Cat, Dog or Human
These may carry disease pathogens that cannot be fully guaranteed to be eliminated during the composting process. There are some advocates for composting human waste (called "humanure"), but the process demands very careful and hot composting.
Plastic, Metal, Glass
Sorry, these simply will not decompose in your compost pile. Check back in a few hundred years to see what state they are in at your local landfill.
Processed foods, bread, colored paper, cooking oil, hazardous waste and milk products should not be composted.