I'll also recommend the City Maps 2 Go app - download maps while still in the States, and also agree with looking at hotels and sites via street view on Google. I spent some time using the street view to locate metro stations, sidewalk landmarks, and the first hotel in Paris before I did the Best of Europe in 14 last year. You'll feel good when you begin to see familiar sights.
For packing, make sure you have sturdy shoes that are broken in. Nothing can ruin a trip quite like sore feet, particularly with the walking that is required. Err on the side of leaving things out if you really don't plan to use them.
From an electronics perspective, I felt that paying the $20 or whatever for a month of international access was smart. Also, if using a smartphone for pictures, make sure you get them backed up a few times during the trip when you have WiFi. If using a camera, take a few memory cards so that all your eggs aren't in the same basket!