I was in search for scalable, sustainable and unobtrusive trading model and I found Short Strangle strategy, which Im pursuing for last six months, which works well in mildly upward trends. My strategy is very similar to what Jvblogger has mentioned and my return expectation is also 4% per month (net of brokerage).
An adequate risk management can never be overemphasized as option shorting is inherently a risky strategy. What I have done is predictive model for return for the entire position at nifty level of +/- 100 points over rolling 7 days. Based on the VIX data available from NSE site, I have found that VIX change has negative correlation of a factor of 6x versus Nifty change. In other words, for every 1% change in Nifty, VIX normally changes by 6% in other direction. I simulate option pricing, for a various nifty levels in +/- 100, along with expected IV at those levels, to compute my expected returns. The desired curve of the return should be a perfect bell curve implying maximum return at current nifty level and lowest returns (or maximum loss) at extreme levels. If this is not the case then there is need to adjust the position.
Its been a constant learning and threads like these further enhance my understanding. The new addition is to correct the position initially through future position (either short or long) before correcting the option strangle. My new strategy is to fix base Delta for strangle short, which I have decided at -0.12. For e.g. delta for short put (Strike price: 5000, expiry: 30-Sep, premium: Rs. 60) would be +0.18 and delta for short call (strike price: 5700, expiry: 30-Sep, premium: 61) would be -0.30, giving a cumulative delta of -0.12. Now, the idea is to delta-hedge the entire position in by buying or shorting the nifty future if there is a variation to base delta. A good link to understand option greeks is
http://en.wikipedia.org/wiki/Greeks_(finance)
My nightmare is huge gap-up or gap-down opening or worst a market circuit. I dont have answer for this. Other than this, I feel the strategy can be followed in the sideways and gradually trending market.