Note: This is assuming new or clean cast iron cookware, and does not include steps for restoring or stripping cast iron.
Place clean cast iron into your oven and heat your oven to 300°F.
Once at 300°F remove pans from oven and use a rag to apply an even layer of Crisco over all surfaces (including handles and exteriors).
Return pans to 300°F oven and heat for 15 minutes. Remove the pans again and wipe them down to remove any excess oil with the same rag.
Return pans to oven and raise heat to 400°F. Heat for 2 hours.
After time has passed turn off the heat and allow the pans to cool in the oven.
If desired, repeat the entire process a second time for an additional layer of seasoning.