What actually happens is the Chicago Board Options Exchange matches to a broker, and the broker assigns to a specific account. If you are called you must deliver the stock. You pay commissions each way. It is quite risky to write naked calls, since the price of the stock could zoom up and you would have to buy it at the market price. In fact, some firms will disallow naked calls altogether for some or all customers.
Puts are almost the mirror-image of calls.
Covered puts are a simple means of locking in profits on the covered security, although there are also some tax implications for this hedging move. Check with a qualified expert. This saves commissions and all that. Paying commissions on those two stock trades gets expensive. Although options offically expire on the Saturday immediately following the third Friday of the expiration month, for most mortals, that means the option expires the third Friday, since your friendly neighborhood broker or internet trading company won't talk to you on Saturday.