How to short sell?

How to short sell?
Short sell is the trading method, in this process first selling of stocks at higher levels and then buying them at lower levels takes place.
Short selling happens in day trading (intraday trading) in stocks.
In Future derivative you can short sell and hold till its expiry which is one month to 3 months based on its expiry date.
In options also you can short sell CALL or buy PUT and hold till its expiry or short sell PUT or buy CALL.
The short selling is done whenever the trader expect for the price to go down.
Any bad news/information would send the stock price at downside.