Don't buy oily coffee beans
"Those oils are lipids. If they're showing [on the beans], that means they're exposed to oxygen, so they'll go rancid. It means the beans have been sitting there a long time."
Don't leave the grounds in your French press
"After you put the water in and wait four minutes, scrape off the top layer of coffee grounds. It's less likely to end up in people's cups -- and the coffee will actually keep extracting once its been pressed, which you don't want. To avoid that, pour it into a separate server."