I think is better to go in the morning... too many people waiting for these monuments. Of course for the Brandenburg gate you don't need to wait in a queue. Enjoy your holidays!!

It depends on what tour you want to go on, but I would recommend Fat Tire Bike tours. They start at 11 am!

Nope

As the others have said there's no need to take a tour. We walked from our hotel to soak up the atmosphere and history and used our guide books and maps . There are numerous information boards around in different languages which were informative ,helpful and FREE! Go and enjoy!

Ah!! As great as Berlin is, it goes to bed early!! The lovely areas I took my family simply shut down after 8-9pm!! I was told there are areas in the outskirts where there are clubs and bars but with young children, I did not pursue these. However, to my disappointment, the amazing areas around Brandenburg gate and Potsdam plaza literally shut shop and become ghost towns!!

It looks like Easter is a great time to visit Germany, since Easter is one of their most celebrated holidays. Many events and special markets and decorations. I wouldn't worry about that.

We found the free tour in a pamphlet at our hotel, but just look for a huge group near Starbucks and you'll find them.

The Brandenburg Gate is always open, but like the other answer, it will be hugely crowded on New Years Eve. If you are using public transit, check the S-Bahn schedule. You'll have to take the S-Bahn to connect. Night buses run all night, but the routes are slightly different and some do not run very often. Taxis are always available.