On what basis traders choose stocks

There are thousands of stocks. But on what basis traders choose stocks. Someone says choose from top gainers and loosers. Someone says choose stocks from top performing sector. And all thousands of stocks have some one would be there for trading even though the stocks are not trending and very choppy. why will someone choose from those kind of non trending and choppy stocks since every trader have technical knowledge.I feel like volumes are fake. Please share your opinion on this

You are Right on this. Chart Reading based on volume is an outdated concept. These days when algorithms are executing at millisecond speed, volume has no significance. Possibly used by institutions to trap people who are new to trading.

Day traders can choose stocks that tend to move a lot in dollar terms or percentage terms, as these two filters will often produce different results. Stocks that tend move 3% or more per day have consistent large intraday moves to trade. The same is true for stocks that tend to move more than $1.50 per day.

maybe choose one which is trending from monthly candles to daily plus the market cap should be above 500billion below that the competition is cut throat

If day trading, trade in stocks that are in the news on that day.