I watched TinTin yesterday (which I had been reluctant too, because it just threw out Herge's awesome graphic style, and then TinTin's voice bleh) and there is no denying that Spielberg can craft a really fun movie. It had me thinking about how Lucas and Spielberg just recreated the old serial movies they watched. So I went poking around and found this fan site that says that they went and watched all 15 episodes of Don Winslow of the Navy for inspiration before hashing out the story. The site says that after their week of day long story meetings Lucas had divided the story up into 60 scenes, each two pages long, and had outlined 6 cliffhangers. So a peril turns up every 20 pages and every 10 minutes the hero is in mortal danger, the danger had to be as real as possible and required the hero's cleverness to escape. Had me trying to pin why Indiana Jones is so fun, but Avatar left me 'meh' and answer I've come up with so far is that Avatar characters feel generic, Indiana Jones the characters are cool and fun to hang out with and feel more developed.
Talking about the Last Crusade it's mentioned that Spielberg storyboards everything, and figures it out on miniatures, which saves a lot of money having it worked out ahead of time and makes it easier for all the different departments to do their jobs.
When Sean Connery came on he really looked to put in as much humor as possible, and as much conflict between Jones Sr. and Jones Jr.
The tank chase was mentioned as being different from most action set pieces because it had more story in it, characters evolved during the chase, we saw Sr. strong for the first time and we see Indy at his weakest.
(makes me think of Lost's approach of couching everything in terms of character.)