First time to London...which area of London would be the best to stay in ?
There is no ONE best area. It depends on several factors. Do you plan to use the Tube/buses (see below)? Where/when are you arriving and departing (Gatwick, Heathrow, other airport, Eurostar train, etc.)? What is your budget (in Great British Pounds)? What are your accommodation expectations (hostel, hotel- how many stars, etc.)? How much walking are you comfortable with? What kind of neighborhood do you prefer(lively, pubs, clubs, etc. or quieter)? The sites in London are not centralized. But you can reach most of them with a Zone 1 & 2 travel card for the tube/buses. If you plan on doing some sites further out (like Kew Gardens) you might need a zone 1-6 card. We have enjoyed staying the Victoria Station area. And have also stayed in the Covent Garden/Neal's Yard area in the past. Both have pluses and minuses. Many on this board also like the area around St. Pancras/ Kings Cross stations, or Belgravia, or Earl's Court, or ..........
Do you have the current copy of RS London Guide Book? If so, great. If not, I would suggest you get one as soon as you can (you can order one elsewhere on this web site) as it has lots of good information that we used when we were making our plans to visit London. As someone else posted, so much of the answer depends on what exactly the traveler is looking for.
We have stayed a couple of times at the Green Park Hilton. From there we could walk to all of the sites although the Tower of London was a bit of a hike. Last visit we stayed in the Bloomsbury neighborhood. From there we could walk to most sites except that the Victoria and Albert Museum was too far. (We usually walk 5-6 miles over the course of a day.) If you use google maps it will tell you how far it is to walk from one attraction to another.
Rebecca - The Falcon Hotel near Paddington Station is nice. So is the Luna Simone near Victoria Station. I cannot speak from experience but I hear Base2Stay in Kensington is also nice. You didn't mention a budget of what are you interestted in seeing while in London.
It's a rare London visitor who does not use the Tube and/or the buses. So, in theory, anywhere you stay that's a short walk from a Tube station or a bus stop will allow you to get where you want to go. Beware, though, of booking "bargain" accommodation deals that are, in fact, near a Tube or a train or a bus stop, but turn out to be a long, long way from your target destinations. A frequent suggestion is to stay inside the area marked out by the Tube's Circle Line route. (The yellow route on this map. It's from the Transport for London site, which is the best place for info, routes, planning, etc., about tubes, trains, buses, etc.) No reason to make that a firm and fixed rule, but I would avoid the hinterlands on that map. (It's not drawn to scale, by the way,