If you are planning on using your pumpkin for pies and seeds (nothing decorative) you can also start by baking it whole for about 30 minutes at 300ºF. The inner steam will start cooking the flesh and softening the rind. After baking, remove from the oven and (very importantly!!) let it cool for half an hour before slicing. You don't want to get burned by the steam that has built up inside. Carefully cut in half and remove the seeds and strings.
Continue baking the two halves, cut side up, at 400ºF for another 45 minutes, or until completely soft inside.