The answer is always the same: Systematic investments over a long period of time.
With tax exemption also available, here is a comparison of 3 favourite investments - Rs. 1.5 lakhs invested each year over 20 years - PPF, ELSS & Nifty.
PPF investment became Rs. 77.82 Lakhs
Nifty investment became Rs. 1.55 Crores
ELSS investment became Rs. 2.28 Crores
Source: Value Research