This is for those of you that might find your self in a museum with dioramas in the near future. Things to remember are that school children will normally be in museums in the mornings until about 1:30. Afternoons are the best time to have halls mostly to yourself. However sketching while students watch can have its benefits as children will say exactly what they think. "Dude that is a cool house!!!""Its the tiger.""Ohhh."
Bringing large sketch boards or sketch pads can be a problem as visitors will bump them. Also if you plan on bringing an easel call first. Many museums do not like to have easels or tripods in their halls.
Bring a bag for you sketch book and other supplies like a snack and something to drink.
The more willing you are to share your art with folks the more cool things seem to happen. I have been given tours of other museum's collections a few times just because some one asked what I was doing and I was open to talking about my love of natural history museums and sketching from their exhibits. You never know when you are talking to some one who loves their work and is excited to show it off.