London - Maps
When in London you need a map!
If you haven't got one already (bought e.g. when you were in london last time:-) you should buy one as soon as you get there. Maps are sold al over the place: at bookstores, in kiosks, by newspaper sellers in the street, etc.
Personally I prefer 'London A-to-Z' but 'Collins' also makes a good map. The 336 page "London A(to)Z" booklet (out of which more than half is the invaluable street index!) costs just £4.95 (June 2000). This is a must-have when walking around in London (which you typically do, walk, in London - a lot!).
But if you're going for the first time and don't have a map already (or if you're just crazy about maps as I am:-) you can do quite a bit of planning using e.g. this London map available on the Net which probably has all the search, zoomin and -out facilities you'll need.
Then, if you want to get know London better I can warmly recommend the 500 piece "London A(to)Z Street Map" jigsaw puzzle that I bought last time over. I believe it improves your "feel" for the general layout of contral London which is useful also when travelling by "the Tube" (check term!). I've done the puzzle already (of course), but I intend to "prepare for the trip" by laying it in advance next time we're off to London.
Doing the jigsaw puzzle you're also "forced" to learn more of the streets of London.