Anyone who knows me, understands my love for science museums. As a kid, my love for scientific research came from curiosity born outside school - in experimenting with a chemistry set that my mom gifted me, in looking at the remarkable Stonehenge on a family vacation and being excited to think about the engineering feat that an ancient people had performed to erect the site. So, I appreciate that space that science museums create for people, of all ages and backgrounds, to learn in an out-of-classroom setting.
In 2011, I also began volunteering at two science museums (the Science Museum of Minnesota and the Sciencenter in Ithaca) usually in the capacity of a demonstrator in concepts in Mathematics and Physics. To be on the other side a lab bench, and see the wonder in a child's, or even an adult's, face when they, for example, see the effect liquid nitrogen cooling causing the shattering of a rubber ball, is beyond gratifying. Learning does happen in these museums, and so I think they are a crucial part of a community, and as such, they should be well organized and presented to create the most impact for the community's benefit.
The science and museum communities can learn best practices about science communication from great science museums. I have been fortunate enough to have been able to go to many museums both in the US and in Europe, two of my favorites include (due to bias I am excluding the Science Museum of Minnesota and Ithaca Sciencenter):
Kontiki Museum in Oslo, Norway (http://www.kon-tiki.no/en/)
The Corning Museum of Glass in Corning, NY, USA (http://www.cmog.org/)
What should immediately jump out is that these museums are not science museums by name! That's not to say that large science museums aren't wonderful (The Franklin Institute is a personal and lifelong favorite of mine), but to show that many aspects of our history can be, in part, explained through a scientific lens.
At the Kontiki museum - a testament to the will and scientific curiosity of Norwegian explorer Thor Heyerdahl - the museum could have just been a retelling of the saga of his voyage through the pacific. Instead, a replica of the craft was created along with a scientific explanation of why they chose the materials for it's creation. They also told of celestial navigation, of how history's human migrations likely took place, and even of how genetic studies ultimately disproved Heyerdahl's theories.
In Corning, at first sound, a museum of glass sounds like an uninteresting tourist trap. However, once inside you are treated to not only a full museum of artistic works using glass sculpting, but demonstrations of glass blowing, a scientific presentation of fiber optics, explanations and examples of Galilean telescopes and Von Leeuwenhoek microscopes.
What's also interesting about these spaces is that they are also not largely known as large museums; they are generally considered local attractions. On the flip side, some of the "science" museums that get a lot of name brand recognition - such as the Smithsonian's National Air and Space Museum, are quite lackluster and, in my opinion, do not leave visitors with an experience rich in learning. In this case, the museum was just a hodgepodge of aeronautical history without a semblance of a coherent story. These museums fall into a trap of a "look at all the cool stuff we have" mentality and regretfully usually lack any type of hands-on activities.
So, in my opinion, what's important to a make a great science museum, or any museum that has a desire to look into their history through science, is not that they have huge, costly exhibits or large collections, or that they be located in NYC or DC or London, but that they have a desire to engage the community and actually teach rather than merely entertain.