The British Tourist Authority  has a USA '800' number.  Phone for maps, pamphlets and brochures.  The first thing you want to ask for is their map of London!  You will not find a better tourist map of London anywhere.

It is very easy to spot Americans who are on their first trip to London.  When crossing a street, they are the ones who... first step off the kerb ['curb'] and then look the wrong way - to the left, not the right! - to look for oncoming traffic.  Think about it... The British drive on the left.  So unless it is a one-way street, that lorrie ['truck'] will be coming at you from your right.

On general principles, you really must experience London's Underground ['subway'] at least once.  But, be aware that it can be very, very crowded!

You will find maps of the entire system at each station in addition to maps of each line in the subway cars.  Also, many of the better guidebooks and London maps have a small size (Bring a magnifying glass!) version of the system map. 

Although you might see the odd ['occasional'] tourist with a rucksack, don't even think of taking full-size luggage on the tube [another name for the Underground.]  We tried it twice and both times it was dreadfully inconvenient.

While the Underground does avoid the traffic congestion above, you will not see very much out of the windows.  If you are on a limited budget, the lack of scenery should not be that much of a bother.

Although very expensive and subject to tail-backs ['traffic jams'] in the city, getting around by taxi has the virtue of allowing you to continue your sightseeing along the way.

London taxi drivers spend years getting The Knowledge ['total familiarity with each and every street'.]  In order to obtain their license, they must know the shortest route between any two points in London.  That does not, however, stop some of them from taking obvious tourists by way of Trafalgar Square no matter where they are coming from or going to.  Personally, if we do not see Trafalgar Square during the trip, I give the taxi driver an extra tip and tell him why!