Tokyo is huge - a combination of cities within a city with no real centre - but it is navigable. For visitors, almost everything of interest lies either along or close to the Japan Railway (JR) Yamanote line, the rail loop that circles central Tokyo. At the centre of this circle is the Imperial Palace, with exclusive Ginza and the commercial Marunouchi to the east. Heading west you'll find food-capital Akasaka next door to clubbers' delight Roppongi, and then 'modern West versus chaotic East' Shinjuku. Ikebukuro is in the northwest, and the cultural centre of Ueno and traditional Asakusa is to the northeast.
In Tokyo, as in the rest of Japan, finding a place from its address can be a near impossibility, even for the Japanese. Few streets have names, so be prepared to ask for directions - don't worry, even taxi drivers do! Addresses work by narrowing down the location of a building to a number within an area of a few blocks; unlike European addresses, they work from top to bottom. So, Tokyo would be indicated first, followed by the(ward), then theor(loosely, suburb) and then the, which is an area of just a couple of blocks: eg, Chiyoda-ku, Nagatachō 2-10-3, Capitol Hotel, 3F. The ground floor is always counted as the first.