Departing from Madrid Chamartin station can be confusing bc this is a major transportation hub with metro in the lower underground levels and both local commuter Cercanius trains in a separate wing and Renfe regional and high speed trains in another. Make sure the tickets are for Cercanius (designated with a red "C" logo, and look for departure times posted on screens scattered around the Cercanius platforms.
It almost goes without saying, but get on the train headed in the correct direction (I may or may not have experienced this ;) as sometimes times can be similar for trains on the same line headed in the opposite direction. What is also frustrating is the station publishes the platform exceedingly late between 3-10 minutes prior to the train arrival/departure so make sure you have your eyes glued on the screen, and are aware of your distance to each platform.
There are a fair number of food and convenience store options in the station at each level, though as another reviewer mentioned outside of seating at the cafes, there is minimal other seating for customers waiting for trains, you basically need to stand around the waiting areas especially during peak times. If you're not familiar with the station and following Gmaps or any other map app, make sure you factor in 20 minutes to find your platform inside after arriving to the station itself, maybe more if you plan to buy tickets within the station, since again it can be a maze. read more