IV can be thought of as the expensiveness of an option due to the expected volatility of the underlying stock. The underlying stock always has the same resultant volatility, regardless of the exercise price of an option, but for reasons unrelated to volatility, options of different strike prices are priced as if there could be varying price movements for the same stock that irrationally depend on it's option's strike price. For this reason, on ETF's, OTM puts are overpriced and OTM calls are underpriced. I would prefer to short options that are overpriced. Shorting ATM and especially ITM calls will have a higher expected return than shorting OTM calls; and with puts, just the opposite is true - the further out, the better to short. Always, and most important, you must use prudent money management: short too many, and no matter how good your expected return, you will eventually be bankrupted.

