What is the best way to dispose of expired prescription drugs?

You're wise to question the best methods for disposing of expired prescription drugs - for that matter, even OTC drugs. The Office of National Drug Control Policy published these Federal Guidelines:

• Take unused, unneeded, or expired prescription drugs out of their original containers and throw them in the trash.
• Mixing prescription drugs with an undesirable substance, such as used coffee grounds or kitty litter, and putting them in impermeable, non-descript containers, such as empty cans or sealable bags, will further ensure the drugs are not diverted.
• Flush prescription drugs down the toilet only if the label or accompanying patient information specifically instructs doing so.
• Take advantage of community pharmaceutical take-back programs that allow the public to bring unused drugs to a central location for proper disposal. Some communities have pharmaceutical take-back programs or community solid-waste programs that allow the public to bring unused drugs to a central location for proper disposal. Where these exist, they are a good way to dispose of unused pharmaceuticals.