Hello,
I will be traveling from Berlin to Munich (one way) on June 30th and would like to take an early train around 6am. Is it a bad idea to purchase my train ticket the same morning I plan on leaving? Or will the seats likely be filled the "day of"? I am hesitant to purchase my ticket beforehand because I like to leave room for error. After checking various websites, it seems reservations aren't required for early morning train rides. Any advice would be much appreciated!
Is it a bad idea to purchase my train ticket the same morning I plan on leaving?
You left it very late so there's not a lot of difference in the fare you can get if you buy now versus the walk up fare; €115 vs €130. See http://www.bahn.co.uk (the official Deutsche Bahn English language website - ignore all the rest except for http://www.seat61.com) for the prices - don't bother with reservations, there are far too many trains on this route rendering it unnecessary.
Only very few trains require reservations in Germany, the worst thing that can happen is that you have to stand in the aisle for a while until somebody with a reserved seat leaves the train, but that is very unlikely.
If you want to save money and see some beautiful landscapes(Elbe Valley, Bohemian/Bavarian Forest) and don't mind travelling all day you can take the EC 171 Berlin-Budapest to Prague, departure 06:46, arrival to Prague 11:27. In the moment 39€ tickets are still available.
Your connection to München departs at 13:15 so you have plenty of buffer time and if your train is not late you can stretch your legs with a short walk in the old town of Prague or just sit down and have a beer or two.
You'll arrive to München at 19:15.
The price of the Prague - München ticket shouldn't be more than 30€ if you follow the advice of the man in seat61:
http://www.seat61.com/munich-to-prague-by-train.htm#.U6Heez9Zrcs
So you can save about 50€ and even have a beer in Prague! ;-)
It takes a whole day however and time is money, so it's up to you whether 50€ is worth to tavel that longer.