The Tokyo City Atlas: Bilingual Guide (by Kodansha) mentioned earlier is a definite must. With it being bilingual you can always ask a local to point out things and both of you will understand.
Also highly recommended is a subway guide. Back in 2008 I used this one
http://www.amazon.com/Little-Tokyo-S...o+subway+guide but it's not available anymore.
You will want a small printed reference you can study ahead of time vs relying only on the wall maps inside the stations. My guide had the intersecting stations for each line marked, as well as station locations for all major landmarks, hotels, parks, museums, temples, etc. Travel time in minutes between each station is also noted to allow calculation of travel time.
Another important note: There are 2 subway companies in Tokyo. The lines are integrated but you need different tickets for each. You can buy a day pass for each individual company or a combined pass for travel on either set of lines.
Many places that deal with foreigners (such as the hotel I stayed at) have detailed walking directions in English from the nearest subway station, with walking time listed in minutes. The system was designed to have most locations within a 10-15 minute of the nearest station.
Another tip would be to carry a small compass to help orient you when exiting a station. Very handy to get back to a station too when you know you are in the right neighbourhood but find yourself walking around in a circle.