1) Planning for retirement is important as one's earning capacity declines with age, making it difficult to maintain their lifestyle without proper financial planning.
2) Various tools can be used to build a retirement corpus, including traditional investment options, insurance plans, rental income from property, and mutual funds. These should be balanced and diversified to reduce risk.
3) It is best to start retirement planning early in one's career to have time to build an adequate retirement fund and avoid financial difficulties later in life. Professional advice can also help in developing an appropriate retirement strategy.