In the US, there is a strategy associated with investing your money called Dollar cost averaging. Essentially what it means is that you invest equal amounts into a given asset or fund spaced out over regular intervals regardless of price. According to Investopedia, Dollar-cost averaging aims to avoid making the mistake of making one lump-sum investment that is poorly timed from a market perspective.
In India, we have an instrument that can help us with these systematic purchases, and it is called a Systematic Investment Plan or an SIP. Like SIPs, there are other methods of systematic investments. For example, just like an SIP helps you make purchases systematically, there is a method to make systematic withdrawals from your investments called systematic withdrawal plan (SWP) and a method to systematically switch from one fund to another called systematic transfer plan (STP).
Many investors have asked me the question of whether it is better to invest their funds as a lump sum or an SIP because they are worried about the market environment. To that I would say that the decision to go with an SIP or a lump sum has a lot more to do with your financial goals and your cash flow scenario rather than the current market condition.
If you have a well-defined financial goal, then that would define the risk-return profile of the portfolio you should invest in. Asset allocation is key to manage the volatility here because for short term goals there will have more allocation to lower risk asset classes whilst longer time horizons can allow for more risk taking if the investor is ok with the volatility.
If you are regularly rebalancing to your defined asset allocation, then the decision to choose between an SIP or a lump has a lot more to do with your cash flows because predicting which asset class will outperform is very difficult ahead of time. In essence, regular rebalancing helps to take away some of the concerns around market timing and volatility.