only thing i can think of besides a platform is a ticket machine, seats and a clock.

it depends of the station level..

In Germany I think there are five levels.

The lowest. Haltepunkt:              One track, one platform, signaling, ticket aurtomat, timetable, clock  and a little shelter for rain
          then  Haltestelle.               more than two tracks and plattforms , signaling, ticket aurtomat, timetable, clock  and a little shelter for rain on each side, sometimes with passenger information system
                   Station ( 3. Grade):  more than two tracks and plattforms , signaling, ticket aurtomat, timetable, clock  platforms are entirely protected from rain, also shops, a control room, passenger information system, Taxi, Bus Station
                   Station ( 2. Grade):  more than two tracks and plattforms , signaling, ticket aurtomat, timetable, clock  platforms are entirely protected from rain, more shops, a control room ticket selling shop,  passenger information system, Taxi,Bus Station
      finaly  main station              more than two tracks and plattforms , signaling, ticket aurtomat, timetable, clock  platforms are entirely protected from rain, a lot of shops, a control room ticket selling shop,  passenger information system, taxi hotel, car rental, and also other features: I.E Stuttgart has a check in for a flight from stuttgart or Frankfurt airport, Pos office, Police, Bahnhofsmission(They help people in wheelchaisrs etc,)
 

 

Andreas

 

You might want to pick your favorite station and start with that for inspiration, e.g., visiting your local station or perusing over photos of a distant station. Pick a station on the scale you are planning on building (e.g., based on number of tracks or number of trains per day). You could then set out to model that specific station or use the features as inspiration for a made up station. Obviously you can't capture everything, so pick the features that appeal to you the most and condense them down to fit the size of your build (most lego station builds are compressed versions, e.g., real platforms can often accommodate 10+ coaches while only the largest layouts could fit that many coaches on a straight track segment). Oh, and of course peruse MOCs and borrow great ideas that  you find there.

There is usually a form of shelter a paved area for loading passengers (not always raised) some benches and lights. Usually a info board of some kind. The smallest station I ever visited was a bus stop shelter and a 30x20 slab of concrete ground level (had to load through one coach and move to your car)