Running and shouting like kids, for sure!
But don't forget that sometimes Miyazaki's movies or anime series he worked are very speedy (I mean, with many characters running everywhere, like the constables in the Sherlock Holmes anime or sometimes in Porco Rosso, etc... It's kinda chaotic but it is one of the different faces of Miyazaki's great work).
Concerning Tonari no Totoro, it is a good way to check that after 2 years of self japanese, you could understand 50% of the two kids's saying
And if my ear is not bad, it seems that I understood that the original ending song is a 'resumé' of the story (but I lack vocabulary
). It is also a very fresh and cool anime, very nice to see from times to times.