Mitaka is reachable from Kanda/Tokyo station (Chuo Line) or ShinJuku Station. The Kanji name for the train station translate directly to "Three Eagle".
Here's my travel log on trying to get to the Ghibli Studio Museum in Mitaka
30/10/06 10:19 am Kanda Station
Waiting for JR train to Mitaka, there seems to be some unusual delay
(chuo lline from kanda to Mitaka takes about 30 minutes)
30/10/06 10:49 am
Somehow my train gave up on going too Mitaka and returned back to Kanda, now I have to give it another try. I missed the part when they announced the train would no longer travel to Mitaka. Of all those Japanese spoken, one of the sentences must mean "get off the train you idiot!"
Hmmm� this must be the right train since another old lady heading for Mitaka is also board
30/10/06 10:55 am
It looks like even the locals have trouble finding the train to Mitaka (seems like some special incidents), I am going to try another one
30/10/06 10:58 am
Board a yellow train following the locals, this train has the three big characters of mitaka printed on its head so it must be the right train
30/10/06 11:38 am
On my way to Ghibli studio, after an hour of delay
as you can see, the trip is pretty confusing.