No opponent is going to be a master of all serves, so you need to be logging their choices in your memory the whole time, finding out their favorites for certain situations. Soon you will start to get a feel for where they like to serve in relation to the score.
The key to returning a serve is reading it early. And for this you need to be staring at the ball while it is still in your opponent’s hand, and learning to recognise what a particular ball toss means. For instance, if someone is throwing it behind them, they are not going to be hitting it flat, and if they are throwing the ball out to the right, it is not going to come at you with topspin. Once you have read it, you need to react. There is no time to wait until the ball is on its way.