If you plan on driving down yourself, there is plenty of parking space available at the temple complex. It is a 45-minute drive from central Jogjakarta. You can hire a taxi from the nearby city of Jogjakarta. It will cost you around 150,000 Rupiah each way, although the price can be negotiated. They are easily available for a day trip from hotels and local travel agents.
Most people prefer coming to the Borobudur Temple by bus as it is comparatively cheap and accommodates big groups. There is no direct bus that goes to the temple complex, so you can take the Trans Jogja 2B bus to Jombor Terminal. From Jombor Terminal, take a bus to Candi Borobudur (which is another name for Borobudur Temple). The bus terminal is a few minutes away from the entrance of the temple.
The best way to explore the Borobudur Temple complex is on foot. A toy train goes around the temple complex for a fee, but it is not very practical to do so. You could also rent a bicycle from nearby hotels or locals if you wish to explore areas around Borobudur.