Yeah you cannot tell if some random new coin is going to be successful or not. Even if they announce great new technology and plans the project could collapse at any point. You should watch projects and slowly start investing in something if you have built up a trust. If you believe in some project, even then invest only small amounts..
The markets are unpredictable and the current market should not be your first indicator of what to invest in. Markets react slowly to great projects and let go of failed ones even slower. And the price changes cannot be predicted, as could be seen with for example ETC. Because of the small liquidity in most altcoins, anything could be pumped/dumped super easily, so that makes almost any investment unsure.