I've seen several times that every altcoins doubles the price in a single day which means every coin or token has its opportunity to boom. IF BTC price does down they drop but suddenly they skyrocket by the next day itself, it's pretty hard to judge which coin might pump for the next day. Is there any specific website which might help me to identify? Kindly share your thoughts.
I'm not sure there is a site that provides 100% accurate information on altcoin price movements. As you rightly noted, prices for many altcoins have been very volatile lately and it is difficult to guess when and which altcoin will show its price growth. However, I believe that you need to take information from services such as Coinmarketcap. To do this, you will need to carry out your analytical work or find an analyst whose information you will trust and will buy and sell altcoins using his information.