To get the maximum benefit of reducing your risk through diversification spread your portfolio across different assets whose returns are not 100% correlated. Different assets should ideally span across different asset classes such as fixed income, equity, real estate, gold as well as different investment options within these asset classes e.g. within equity shares, your exposure should be to companies in different sectors; or within fixed income investments, partly government risk and partly corporate risk.
As a thumb rule, diversify your investments across 15-20 different portfolio holdings if you are directly investing in stocks or bonds. If you are investing through mutual funds, then three MF schemes for stocks and three schemes for bonds should provide you adequate diversification
Source :Moneycontrol.com