steam vs. bake a sugar pumpkin
The best method, for flavor development and low labor, is probably to simply roast the pumpkin.

Derobert has written a blog entry describing this in great detail.  With pictures!

Cut the pumpkin in half, scoop out the seeds and guts, and then roast (cut side down) on an oiled sheet pan at about 425 F for about an hour (optionally turning face up to brown slightly at the end).  Let cool enough to handle, then scoop out the flesh and puree in a food processor.  Derobert then recommends a second roast, spread out in a sheet pan at 350 F to reduce the water content--it is done when it darkens slightly or shows cracks.