We have to get to the train station in Madrid for the 7:30 am train and I didn't realize the station is supposedly so large. Any tips? Probably grab a cab. We have our tickets printed... can we just board when we figure out the track etc?
Puerta de Atocha station is not particularly large. From where a taxi will drop you to the waiting area is only a couple of minutes.
For a high speed train you will need to go through the X-ray security to access the waiting area. Your luggage goes through a scanner like at an airport and you usually just walk through. I have been wanded by security but most people just walk through. It seems a bit hit and miss about whether you need to take your jacket off. You don't need to get out liquids or electronics/phone etc.
Track numbers may or may not be listed in advance but you usually won't be able to access the track until around 15-20 minutes before your train is due to leave.
Your ticket (and possibly identification) is checked before you go down an escalator to the track platform. When they check your ticket ask where your train carriage (coche) will be as some trains are 20-plus carriages long.
It sounds cumbersome but moves pretty quickly. The longest line we encountered for X-ray machine was maybe six people. Once it's time to go down to the track Renfe will have four or five people checking tickets using handheld devices. Just join the line and wait your turn.
I will add that when they check tickets, they actually scan the QR code. Most people I saw had them on their phone but a few had printed tickets. Just make sure the QR code is in good condition and scannable.
Adding some thoughts-
-The total Atocha complex is large, but the old part, the brick building, is barely part of the working station. Approaching on foot is more confusing and more of a trek, but a taxi would drop you closer to where you need to be. (the metro station is also closer to the actual trains.) I target arriving at Atocha 30 mins before my scheduled departure—sometimes I have time for a coffee inside security, and sometimes a delay en route or a line for security eats the 'fudge factor'.
-When the track is announced there will be a bit of a rush to get in a long line (or two). No one in line gets left behind. If you get in line for the actual track and they open the booth for the neighboring track at the same door and platform, feel free to jump to that shorter new line.
-If the train is made of two sets coupled together, the car numbers will be 1-8, 11-18—but maybe the reverse of that order. Car numbers are on the digital displays in or next to the car's door. I don't remember why, but I found that a little confusing the first time.
-If you plan to take a cab from the station in Granada, I'd suggest you hustle off the train. Not, like, pushing old ladies, but no dilly-dally. The line at that cab rank gets looonnnngg.
-If you're taking a train out of Granada you won't 'pre-clear' security like Atocha. Rather you'll line up for security as you head to the platform.