. . . skip the Archeological Museum in Anuradhapura. Many of the objects in the musuem display aren't that much better preserved that the objects at the sites. We politely refused a tour and were left to our own devices with limited informational signs.
With so many things to see in Anuradhapura and the time it would take for a proper tour of the museum, you may find your time better spent other ways.
When visiting the Ancient City pay attention to the monkeys. Especially if you will buy peanuts for them. Not all of them are friendly, some could became very agressive!
Basicly there is two kinds of monkeys in Sri Lanka (and in the Ancient City) - one with "white" faces, and another with "black" faces. And the first ones are to avoid. The second you can feed.
At the Buddha Samadhi, a sign warns tourists from standing with their backs to the statue while being photographed.