Well, a lot of TT learning is really exposure to scenario and adaptation through some mix of trial and error or coached feedback. So just facing serves will answer your question to some degree but here is the logic:
To serve really fast, a serve has to come fairly low and fast through the table. To do that, it has to cross at barely net height and bounce low. To do that, it needs a bounce close to the endline on the opponent's side so it can come at you fast. In fact, to serve faster in general, whether short or long, you need to serve closer to your endline.
Usually, the spin and the depth of the first bounce on your side from the opponent's serve will determine whether it is short or not. Sidespin gives a longer path through the table and backspin tends to slow down forward momentum, but they can still go long if the bounce is too deep or there is too much energy on the ball. But if the serve is not extremely fast, which you will be able to tell from the first bounce on the server's side, then you have time to look at and guess and assess the rest. It is the situation that rushes you extremely that you need to be prepared for first and foremost. In TT, as with most things, training tends to make you guess faster and make you more comfortable as you see that things are really not as fast as you think. Usually, the faster a serve, the more likely it is to come long unless the server is extremely skilled. But even slow serves drift long or at least drift attackable, especially down the line. And many shortish topspin serves drift long as well.
One of the tips a top coach gave me that helped me a lot over time was this: if you are using short serve returns (pushes, flicks) and you are repeatedly making errors in the serve return, you are likely using short serve return techniques on long serves. One of the reasons my why game is uncomfortable for adult opponents is that I attack a lot of serves that many players push because the push is very overused to return serves at intermediate adult levels. People just don't realize that a lot of serves are loose if you practice attacking half long serves a lot.
A lot of this is really just ideas to fuel better judgment, ultimately practice is practice, there is no perfect substitute for it. But if you learn to loop balls relatively late as opposed to jumping on them right after the bounce, you will be able to loop many serves with confidence and your ability to read them will improve.