A lot of calls will be "covered" by whomever wrote the option initially, meaning for each contract they wrote, they hold 100 shares of the underlying security as collateral. I don't know the percentage and my Google skills are failing me, but perhaps someone more familiar with the industry can comment on the ratio of covered v. naked calls.

I've written cash-secured puts and covered calls a decent amount as an individual investor, the worst thing that happens is you end up buying something for more than it's worth or selling something for less than it's worth. However, it rarely goes wrong the first time and you've made premium from other options many times over on the same security. If you look up the Wheel or Triple Income options strategy that goes into the specifics of it. It works pretty well for high-volume, stable stocks that you want to own anyway.