(1) Don't try to use them or sell them. Its illegal and dangerous.
(2) Don't dump them down the drain or flush them down the toilet. It is also illegal in many jurisdictions and can contaminate the water supply. Not a good legacy.
(3) Don't crush them or grind them up. Some people do this thinking it will avoid misuse by others but many prescription drugs, especially those treating HIV and cancer can be dangerous to inhale in particulate form. In fact, it is best to avoid touching medication you are unfamiliar with unless you are wearing plastic gloves.
(4) Don't think you are required to take them to a take-back center for incineration. It isn't legally required and most research suggests it isn't worth the time, money, or emissions.
(5) Do dump all medications out of their original containers and into zip lock bags containing used coffee grounds or used kitty litter. This will help keep them out of the reach of kids, dumpster divers, and animals. Seal the bag and dispose of them in the trash. Use a sharpy to cross out all personal information on any prescription bottles and/or crush the bottles to avoid their being illegally refilled and/or being used for identity theft. Toss the seal bags and containers in the trash. This is consistent with the FDA recommendations and Seattle disposal advice.