Izmir has a well-developed transportation system that makes it easy to reach from different points of the country.
Izmir Adnan Menderes Airport is located in Gaziemir, a convenient area for transportation to the other districts of Izmir. There are direct flights from many countries to the airport. Many other airports in other Turkish cities also have direct flights to Izmir.
Transportation to Izmir city center and other districts from the Airport can be done by taking subway, bus or taxi. There are also minibus (dolmus) services from different districts of the city to the airport. You can go to our post on how to ride a dolmus in Turkey.
You can take ferries between Karsiyaka and Konak. It will help you to shorten the transportation time while having a good experience.
Izmir Bus terminal is a major one in the region having bus services to/from almost all cities in Turkey. After you get to the terminal, you can get metro or public bus to the districts of Izmir.
If you are coming to Izmir for the holiday resorts, you can get any of the buses leaving from the bus terminal in that direction. There are services to all holiday resorts from there.