The main factors are basically two. One is the trading volume which you can get from coinmarketcap website and the second one is the market cap. A decent amount of market cap is sign of a good currency and also if the trading volume is high, the price of that currency is most likely to go up. There are few other factors as well but these are main two factors to look for. Higher trading volume means that a lot of people are interested in that currency  so it is mainly a popularity indicator. The more popular a crypto coin is, the more higher the price can go. Also if you see a sudden increase in the trading volume of a particular currency, it means, the price can go up quickly and you can make some quick profit by entering at a cheaper price. Coinmarketcap website is a good resource for these info.