Alt coins are priced in BTC terms so normally they will follow BTC up or down depending on the fluctuations of bitcoin itself. However sometimes alt coins will diverge from the price of Bitcoin when they have active development, e.g. a second exchange listing, release of a white paper or an updated wallet. So its best to keep an eye on the alt coin team and their activity for a coins you are interested in. How active are they on github? What have they done recently for their ecosystem? Coins can go very far with social media alone, look at Dogecoin, it is not known as a highly technological advanced coin and yet the DOGE market cap has snowballed.