Hi Vikki67.
I posted a similar question a couple of months ago and got some useful answers. Here is the link.
http://www.theanswerbank.co.uk/Travel/Question 488574.html
I really enjoyed Berlin. I agree with tyrepill - it is very easy to get around however we bought a 3 day ticket which worked out as better value than the daily one. Both allow you to travel on all public transport ie the trams, the train (S-Bahn) and the underground (U-Bahn).
The reichstag, brandenburg gate, jewish museum, fernsehturm, and the museum at checkpoint charlie are all worh visiting.
The city bus tour is worthwhile taking early in your trip to help you get your bearings and to give you a chance to hop on and hop off at popular tourist sites.
If you like shopping then KaDeWe is worth a visit - particularly the food floor which goes on for ever with a huge choice. Try experiencing some traditional Berlin food. The locals are more than happy to advise you.
I don't know if you can speak any words of German but using a phrase book to help with a few of the basics is very much appreciated by the locals.
There are a couple of weekend flea markets which are worth having a look.