Thessaloniki Makedonia airport may not be the best of airports. The terminal building is fairly small, it is dark, cramped and starting to look quite old. But there is a great thing about it if you fly Aegean Airlines (or Olympic Air) and have access to the Aegean Airlines Lounge, which means you are either a business class passengers or a Star Alliance Gold card holder. There is boarding from the lounge!
There are no passengers bridges at the airport. All aircrafts use apron parking positions and passengers are taken to and from the terminal by bus.
When it is time for boarding for an Aegean Airlines flight one of the lounge attendant will pass through the lounge to announce the boarding and of course the destination. Then he or she will open a rather discreet door by the panorama windows in a corner of the lounge where there is also a counter with a boarding pass scanner.
After having had your boarding pass scanned you pass through the door out to the terrace and descent to the apron where the bus will be waiting, a separate one for premium passengers. Boarding for the other non-premium passengers is done at one of the regular gates in the transit hall and these passengers will board a different bus, most likely far more crowded.
And with a bit of luck the premium bus will arrive at the aircraft before the regular bus, which means you can take your seat without people pushing behind you, and there will be space for your hand luggage.