Take the S- and U-Bahn to get to the Wies'n:
Experience shows, that public transportation systems are the best way to reach the Oktoberfest. Even if they are very crowded during the Fest both, S- and U-Lines are capable of dealing with the enormous masses. Depending on the particular line the train service starts in the early morning and ends shortly after midnight.
S-Bahn: S1 - S8 to station "Hackerbrücke" or S7 and S27 to station "Heimeranplatz", and further on with U4, U5
U-Bahn: U3, U6 to station "Goetheplatz" or "Poccistraße". Alternative U4, U5 to "Theresienwiese" or "Schwanthalerhöhe".
As 'Theresienwiese' is usually the most crowded station, locals try to avoid it and prefer the alternatives "Schwanthalerhöhe" and "Poccistrasse". Visitors from suburbs should keep in mind, that the last trains leave the town short after midnight.
Parking: It is nearly impossible to find any parking in the vicinity of the Theresienwiese. So the best way to get there is by Munich's public transportation (Park & Ride) or taxi.
Normally it is easy to catch one of the numerous taxis around the Theresienwiese. But don't forget, that you could encounter problems doing so from 10 p.m. on, because of the masses leaving the fest each night.