London Museums: The National Gallery
The National Gallery is home to many treasures and some surprises in the least known galleries too. Since it's one of the more popular museums and most accessible, it can get a bit crowded so best to come early so you can have the famous galleries all to yourself and then you can move on to the other areas once people start coming in.
You can also sign up for the free tours. Many times we found ourselves sitting in one of the benches and listening in to the tours for students. It's especially nice to hear also how the young minds interpret the different artworks. To each his own, so find out what's the best way for you to truly enjoy what The National Gallery has to offer.