Making things more realistic in Flight Simming is very easy to do.

Assuming you have loaded up the Microsoft Flight Simulator  you have the base to build on.

 The first thing you need to do is get yourself a decent airliner to fly. The Level D Boeing 767-300 is a great aircraft to fly first. Learning how to program the flight management computer takes a bit of time to learn but well worth it. PMDG products 737, 747 and new the 777 iflys 737 are also very good. These websites can be found by using search engines. Airport Scenery is next on your list Aerosoft have designed some very realistic airports at reasonable prices and for the UK Scenery xtreme. If you go to AVSIM.COM  and you can find hundreds of  freeware aircraft, sightseeing scenery and airports. They are easy to install. In fact the whole of our virtual airline destinations can be found in these sources alone. A decent flight planner is needed for ease. I recommend Aerosoft PFPX but there are free route planners and fuel planners in the internet . Having made your flight plan with this I suggest you get a decent weather program. For this I recommend Active Sky Weather using the flight plan  you created with Flight Sim Commander. This program downloads the weather using stunning weather graphics making it realistic. If you have Ground Environment Professional this will load textures to suit the weather on the ground such as cloud shadows snow. etc. All you need then is a decent Air Traffic Control program.  For this I recommend Radar Contact 4. Again from your flight plan it gives ATC  gives you instructions all the way down to your  destination. A program called Fs Passengers could also be used to simulate the airline operation giving you sound effects and passengers. With all these programs you cannot get it more real than this. For ground services there are AES from aerosoft you have then all the things you need jetway follow me's cater trucks passenger busses and much more or alternative GEX.