Cracking choice of venue, it's a great place - lucky Mrs LordSplodge!
Travel: Get a BVG 7 days pass for zones AB, costs around 26 euros and lets you travel on all trams, trains, buses and u-bahn lines. It's utterly superb, good enough that you need never worry about taxis etc. You can buy the tickets from the newsagents at the airports, the first time you get on a bus/train/tram just validate the ticket in one of the machines. (there are no ticket barriers at all.)
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Thing to do:
It's a big city, and fairly spread out. I preferred the East much more than the West, the areas around Alexanderplatz are good fun to walk around and browse etc. Things you definitely need to see:
Checkpoint Charlie (FreidrichStrasse) - The museum is a bit of a mess but still worth a look, as they have a lot of the weird contraptions that people used to try and escape over the wall with on display. Try and get there before 9:30, it gets VERY busy with tourists etc.
Hackescher Markt (just nW of Alexanderplatz) - a really cool little area that has shops, cafes and bars by the truckload, it's easy to spend a day wandering around this area alone.
Bergmannstrasse (off Mehringdamm) - Bohemian area with a load of cafes and cheap restaurants. Mrs Goliath and I ended up spending three nights in a row here, it's great just wandering from cafe to bar, having a 5 euro cocktail in each and then forgetting how to get back to the hotel
Brandenberg Gate and the Bundestag - great to wander around, but again get there early to beat the crowds.
Berlin Wall (Bernauer Strasse) - not much of it left, but there is a good stretch left here along with a small museum.
Kaiser Wilhelm Gedächtniskirche - A shining example of what our plucky RAF boys are capable of
There is rafts more to do than I've described, it's a big city with a lot to see. You'll love it.
