Items like ads and vents could only be built on concourse walls, but walls are scarce. If you have a huge concourse, you can consider removing 1x1 floors in the middle of the concourse to build some pillars, that way you can hang four ads or put some vents on the pillar. Note that these pillars would block light sources.
Do not over expand your station
Overexpanding is something that players prone to do but do not realize is harmful to their station, if your station is flooded with commuters, you are advised to close one of the entrances, or set them to exit only (yes you can actually do that), otherwise overcrowding and the spread of disease could make you lose reputation really quickly. Setup alarms to evacuate commuters if a pandemic outbreak is out of control. Do not attempt to hold the alarm and move them around after building one, because that does not work, and would trigger the alarm. Sell it instead and build a new one.
Invest in Level 2 trash bin early
Though Level 2 trash bin only increase the capacity by 5, but it is 50%, and doing so actually make your commuters left prone to littering (not sure if it is true of simply because the bin are less prone to full). Micromanage your staffs to clean the bin when they are 50% full, because full bins would generate noxious fumes, which is harmful to both your staffs and commuters.
Invest in lights and carriages early
Commuters do not like gloomy stations, lighting is a must have when you start off your station. Investing in more carriages and newer stocks would increase the throughput, and hence reducing overcrowd problem. When you have a big train, you would like to send off the very first train after passengers alighted as passengers would not board the train anytime soon. Once they are ready to board the train, another train would be arriving.
Maintenance
Machines like turnstiles, ticket machines have a condition value, they could be seen by hovering your mouse on them. With a staff equipped with tool kit, you can actually maintain these machine before they potentially break. This is good for both your station and your staff, as repairing a machine takes very long, causes noxious fumes and would reduce your station's reputation. Regular maintenance of machines would grant your staff experience, reduce the time to fix a machine, prevent the generation of noxious fumes, and keep your commuters happy.
Plan ahead
If you are an accomplisher, and would like to have all of your station reaching 5 stars, you might want to spend 5-10 minutes planning about where to put your platforms as you cannot overlap platforms and concourses in this game. Once you opened the station, there is no going back, unless you abort challenge.
Save bonds and money for new procurements
Some players might tend to use up the bonds whenever they have something unlocked, actually this is unnecessary, because not all of them are of immediate use. Sometimes this could kill you off (you might not lose the station, but could cause some serious troubles). It is a common mistake to spend all the bonds and suddenly a commuter with cardiac arrest pops up (oops). A good practice is to check the to-do list on the top right hand corner, if it ask you to build a rat prod, your station is probably gonna be infested with rats very frequently, that way you can prepare for it.
DIY some pillars...