You take the Train from the Main Train station in Munich……. the trip takes about 2 hours.The trip is pleasant not spectacular but a nice way to spend 2 hours.
When you arrive at Fussen the closest town to the Castle a Bus is waiting for you outside the Train station it is about 3 USD but included if you have a Bayern ticket.The ticket can be purchased online or at the train station it is about 28USD and can be used anywhere in Bavaria including Saltzburg for almost 24 hours for any type of public transportation.I used the Bayern ticket to go on the U-Bahn to the
Munich central station………. it was used to go to Fussen and then showed it to the driver for the 30 minute ride to the Castle.You arrive at the bottom of a hill to get to the Castle which has its own shuttle to the top……. are you tired yet ? This is a long trip and a lot of people are making a buck from this Castle especially Disney.
But you get your reward when you start to get a view of the Castle and of course you pay again if you decide to go into the Castle.Although the views of the area are nice I think just walking around the area and getting a view of the Castle and the area is more interesting.
My suggestion is to arrive early and try to come in off season.Even though it was late April it was still busy.Also it was about 45 F or 7 C not a Beach day.