Edinburgh Castle is spectacular - bring a camera - you'll get fantastic views of the city
If churches are your thing, (I like the architecture of them) there's a big cathedral on high street that's stunning, i just can't remember that saint it's named after
The Royal Mile is a nice walk that takes you past all the "must see" places in Edinburgh -
The scotch whiskey heritage center....
http://www.whisky-heritage.co.uk/
Wear comfortable shoes, you will walk the soles of your feet off, this is not the trip to wear new shoes. Be prepared for any kind of weather. The people are friendly, the pubs are plentiful, the public transportation in the city is real workable -
Stay away from Haggis - -that stuff's nasty