Poznan can be easily approached by several ways:
Lawica Airport in Poznan is connected to major European cities by flights operated by both low-cost and national airlines. There are direct flights to Poznań from more than 20 cities in Europe, including Barcelona, Bristol, Eindhoven, Glasgow, London, Malmo, Milan, Oslo, Paris and Warsaw. It may be also worth considering to fly either to Warsaw (to Chopin Airport – mostly national airlines, Modlin Airport – budget flights) or Berlin (Schönefeld or Tegel Airport) as both of the cities have frequent and fast train and bus connections to Poznan. For the information how to get from one of these airports to the railway stations, please check their websites.
There is a train from the main railway station in Warsaw (Polish: Warszawa Centralna) to Poznan (Poznań Główny) every hour. The travel takes between 2,5 and 3,5 hours and costs around 60-120 zloty (roughly USD$15-31). The tickets can be bought either at the ticket counter at the railway station or on the internet here. There are also four direct trains from Berlin (Berlin Hauptbahnhof or Berlin Ostbahnhof) to Poznan every day. The approximate time of the journey is 2,5 hours and the cost equals between 19 and 45 euros (approx. USD$21-50) ( (booking the ticket in advance might make it cheaper). For the information about railway routes between Poznan and any other cities please use one of the above links.
Another way to get to Poznan is by taking a bus. Polskibus offers tickets from/to both Berlin (3 hours, 15-120 zloty (approx. USD$4-31)) and Warsaw (4-5 hours, 25-100 zloty (approx. USD$6.50-26)), many other Polish cities but also Prague, Bratislava or Tallinn. You can also have a look at offers from companies such as Sindbad or Simple Express.