We opted for one of the Jeep tours from the visitors centre.
I expected an informative guide that would explain the geology, the history of the Navajo nation. We didnt get any of that, in fact our guide didnt know much at all about local history or the area. Sure, we saw the wonderful formations and were taken to areas not open to normal cars, but I was still left a little disapointed and I would liked to have learned more. He did sing us a couple of songs, which were OK.
I was also disapponted to find out that prices have doubled in the last couple of years.
If you have a decent 4WD, then consider driving in yourself. You will see 80% of the sites we visited - just take your time as the road is more rugged than many expect.