If you do not select right stocks in Intraday then it will not make you a professional trader. Like Intraday strategy, Position sizing and Risk management, selecting right stocks in Intraday trading is crucial to success and remain profitable. The most simple and common approach is to select the stocks from the Nifty Top Gainers/Losers because it provides the stocks which are traded for the day as they have been in the Top Gainers/Losers. If you wish to check out the Top Gainers/Losers for today below link is for NSE website.
Apart from that you need to have quick look to the Nifty Advance/Decline Ratio for gauging the Intraday trend of Nifty. There are some specific values of the Advance and Decline which provides a comprehensive and quick picture of the trend of nifty. Depending on that you need to focus on the Longs or Shorts i.e Gainers or Losers. To have the Live Advance/Decline ratio, below is the link for the site which provides it.
In this video, I have explained how to select stocks, maintain watchlist and take trades.