Alfred, when you buy a call option from me, you have the right to buy the underlying stock from me at a certain price before expiration. Since I sold you that option, I have the obligation to sell you the same stock.

So if you sell an option, you have an obligation that is in force until the option expires, or you buy back the option. Since you have an obligation, you have to understand how you are going to cover that obligation. For example if you simply sell a June 650 Call on AAPL, you have the obligation to sell someone 100 shares of AAPL for $650/share. If AAPL spurts to 750, you have the obligation to sell at 650, so if you don't already own the stock, you have to buy it at 750 in order to sell it at 650. The moral of the story: whenever you sell an option, you have to have a plan to cover the risk.

You can cover the risk of that June 650 short call by a) owning the stock already, b) buying a June 660 call so your max risk is $10 per share, c) buying a July 650 call, etc. There are many strategies to cover the risk of selling a call... and selling a put.

My favorite strategy is the vertical spread where you always buy an option in the same month a striker or two away to help you cover the risk of the short option. It's a flexible strategy with many permutations. My new book, mentioned below discusses a longer term vertical bull put spread. You might enjoy it.

I'll agree with AC above not to sell options until you understand how and why they work. But I don't worry so much about options that expire after earnings. I don't mind you opening those trades. Just be sure to close them a week ahead of earnings... until you know exactly what you're doing.