Poznań’s main train station (Dworzec Poznań Główny) is opposite the Trade Fair Centre and about 10 minutes by taxi to the main square. The site of a massive 160 million złoty redevelopment project over the last few years, a new transportation centre has arisen alongside the old train station building, creating a strange clash of deep People's Republic and shiny 21st century - the latter packaged in a breadbox shape, as critics have sneered - with train platforms scattered confusingly between the two. Allow extra time to locate your train, and woe to those departing from the notoriously difficult to find platform 4a - reach it by following platform 4 (in the old section) to the very end, away from the trade fair grounds. If you see 4b, you've gone in the wrong direction.
But back to the breadbox: modern and state-of-the-art, it finally integrates rail, tram, and bus connections in one squeaky clean transit station. As a result, this is now the point of entry for most visitors to the city, including those arriving at the airport and taking the direct bus to the centre, which drops off here. In this day and age, it's practically impossible for any new train station in Poland to not come prepackaged with a shopping centre, and that is certainly the case here: welcome to Avenida, a shopping haven with a food court and parking for 900 cars, plus additional opportunities for consumerism and refreshment spilling out into the train station hall. Other now-standard amenities include lockers for large luggage (have some coins handy), currency exchange, and bank machines. The city of Poznań operates a tourist information desk, but there's also the PKP-operated Train Station Office (open 07:00 - 21:00), which can help you plan your trip, get tickets, and even get into town.
Normal ticket windows are conveniently open 24hrs, but using the ticket machines (which have English options) is just as easy. If you’re running late, note that it is possible to buy tickets onboard the train from the conductor for a small surcharge. Check the timetables online at the Polish railways website - rozklad.pkp.pl - which has good English functionality; if you want a seat on a particular train, it is best to book ahead.
Taxis await you immediately outside, and a ride to the main square costs about 20-30zł. Alternatively, hop on tram number 5 (to 'Wrocławska') or number 8 (to 'Pl. Wielkopolski') from the ‘Most Dworcowy’ stop located on the bridge, and you will only have a short 6-7 minute walk to the main square; a 10-minute ticket will suffice.