In my personal experience, a simple approach to investing works the best. The simple idea that works is to invest regularly at all times, invest more when valuation is attractive (NIFTY PE less than 18.6) and take some money of the table when valuation is expensive (NIFTY PE >22.1). The below points illustrate this:
1. Keep investing at all times in equity. You have to be “in” it to have a chance to “win” it. Given the fear of sharp correction and our natural inclination to invest at the bottom, we all tend to suffer from decision paralysis. As a result, we never have a decently good allocation to equity. Now equity returns don’t move in straight line. There could be prolonged period of flat market. Rather than being disappointed with lack of returns or equity underperforming fixed income assets, this is the time to sow the seeds. Keep investing because when the tide turns, one must have decent allocation to benefit from higher return.
2. Top up your investing when valuation is cheap. Whenever valuation (For NIFTY PE average PE is 18.7) is below average, it’s a good idea to top up a SIP or start a new STP from existing fixed income mutual fund holding. When equity valuation is 1 standard deviation below historical average (NIFTY PE of less than 15.2), equity allocation must be high (at least) 75%. 
3. Book profit but continue the SIP when valuation is rich. When NIFTY PE is more than 22.1, it is better to book all your long term capital gains and shift the money to a liquid fund. However, even at this time don’t stop SIP. This booked profit should be used for equity investment when valuations head towards historical average. We can get NIFTY valuation data from here. This is a way in which one can look to boost his returns above the market returns. We do not need to do this every week but once a quarter should give an idea about valuation and necessary action if any.