If I may chime in . . .
I am an experienced options trader. A naked call or a naked put is a very directional "bet" that a stock/index/ETF will move a certain distance or not move a certain distance in a specified period of time.
I used to trade these especially just before expiration Friday. My thought process was what could go wrong in just a couple of days? As I found out, plenty can go wrong! I was once on the wrong side of a naked call and a separate naked put just before expiration and it cost me 10% of my account.
It is very easy to mitigate the risk of a single call or single put by buying a slightly different strike for the same expiration. This is called a credit spread. While the reward is much less, the risk is MUCH more manageable. Credit spreads (either a pair of calls or a pair of puts) are easy to learn and to trade. You can manage the risk to near zero by buying your sold strike when it gets cheap enough before expiration. I buy the sold strike for volatile underlyings (GOOG, AAPL, RIMM, etc.). I don't bother for more stable underlyings (SPY, SPX, DIA, QQQQ, etc.).
In sum, selling a naked call or a naked put is gambling. No amount of analysis will give guidance. If you like to live dangerously, play naked on biotechs just before an FDA announcement. Whoo hooo! Better than any roller coaster I've ever ridden. You won't sleep while you are sweating the outcomes.
Also, buying a call or a put with proper analysis and selling it for a profit can be a good income strategy. There are many ways to play this strategy. Buying ahead of earnings announcements and then selling just before or just after the actual announcement event can generate good returns!