Booze is the same price as in Belgium or Amsterdam. Go to the Reichstag, but get there as it opens to avoid a 2/3 hour queue. If you're there for a night go up the Fernsehturm about an hour or so before it closes, you get a panoramic view of most of Berlin which is amazing at night. Also the bartender who works there is an awesome dude. Go on a free Berlin tour which takes up most of a day and then go on the bar crawl at night, if you go on the tour you get a discount on the crawl. Tip your tour guide about 10 euros though, they live off tips and have to give the first 1/4 or so to the company.
Most importantly, stay at the Wombat's youth hostel. It's probably the best damn hostel I've ever stayed in. Book here:
http://www.hostelworld.com/hostels/Berlin
Go to checkpoint charlie if you really want to but (a) it's covered in the free tour and (b) it's all fake. It's just re-built Disney-esque over-crowded tourist bullshit.
If you're going out at night looking for a good time just avoid the west altogether and hit the east, I can't remember any road names but ask around and there's plenty of atmospheric bars filled with great people. If you stay at Wombat's there's a bar on the roof which is open every night where you can buy extremely cheap beer and sit out star gazing/having a BBQ/watching the city lights.
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Massive, epic adventure, multi-coloured, multi-layered.
Sort of two/three dimensional Wizard of Oz for the future.