Stock market is subject to fluctuation. Those which may fetch good returns today may not be fetching so after a few years. The contra also may happen.
However shares of companies which are established and have a good history strong financial parameters like strong capita and , reserves, growing turnover, growing profit, steady and consistent dividend payout, issue of bonus shares if any, healthy trade in the stock market etc are safe to invest in.
Then there are certain sectors which are always essential and in daily demand. Investing and staying invested in them is good. However there are certain sectors and industries which get boost and encouragement by the changing policies of the government.
Just for example, after the currency withdrawal recently, there is a boost for the online payments systems and online wallet systems. The manufacturers of point of sales machines may get a boost in turnover and profit.
Generally it is safe to invest in established companies with reputation and good capital spread and market trade volume. One should not expect overnight windfall, but keep patience and stay invested for some time.
So one should keep watching such upward trends and downward trends in sectors and related companies. In case one is not that much knowledgeable and experienced, it is better to invest in established mutual funds . Here one can select sectorwise funds or diversified investment funds.
It is suggested that one may follow one o two market channels and one or two financial magazines.