On my list of world heritage sites, Hawaii Volcanoes National Park is listed as my very first site. When I began traveling full time in 2007, my first stop was in Hawaii, and my first stop in Hawaii was the Big Island. 

I had previously visited here in 2006 on a geology field trip, so I guess that would actually be my first visit to the park. 

This is probably the best place on Earth to see lava and volcanism, however, your ability to see really good lava flows is going to be dependent on luck and when you happen to be there. Unfortunately, I never saw flowing lava during any of my trips. 

This is one site where to have the best experience, you should pay attention to the news and show up when there is activity going on.