By plane
Pula has its own international airport (http://www.airport-pula.c...) with daily flights to Zagreb, and direct services from many European cities including Amsterdam, Edinburgh, London, Manchester, Oslo, Vienna and Zurich. Ryanair operates direct flights from London three times a week. Many flights to Pula are charter rather than scheduled, while other flights are seasonal summer only.
There is a scheduled bus service from the bus station in town to the airport. Buses are operated by Brioni (http://www.brioni.hr/brio...) and connect to most major flights. The cost of a one-way ticket is 25kn. A taxi from the bus station to the city should be around 85 kuna in the low season and much higher in the summer.
It is possible to also consider Rijeka Airport (http://www.rijeka-airport.hr/) on the island of Krk and Trieste Airport (http://www.aeroporto.fvg....) in nearby Italy to access Pula as they are close by and offer flights to different destinations.
By Sea
Hydrofoil services operate from the wharf both around the Croatian coastline, and across to Venice. These are pricey, though provide a quick journey and provide some great views.
Venezia Lines (http://www.venezialines.com/) ferry connects Pula with Venice. It runs five times a week, travel time is around 3hr.
By road
The large and modern bus station is on the edge of the 'old town' district and is the hub of local, domestic and international bus routes. There are direct buses from Zagreb, Rijeka, Split, Trieste, Ljubljana, Belgrade and Venice. Online timetables are listed at (http://www.brioni.hr/brio...) and (http://www.pulainfo.hr/en...).
There is also a train station near the waterfront with services serving Istria and into Slovenia due to historical circumstance rather than back towards the rest of Croatia though a connecting coach service operates for services to Rijeka and Zagreb. Ticket prices, timetables and other information are on the Croatian Railways (http://www.hznet.hr/) website.
Hitchhiking from Zagreb works very well. In Zagreb start from the petrol station after the "Billa" supermarket on the southside of the Sava river. In Rijeka ask people to drop you off at the little SOS stop after a pretty sharp right bend of the motor way around Rijeka.