Check the back of the sunflower blossom heads for the proper harvesting color. If the back of the head is still green, the plant is not ready for harvesting.
Check the back of the sunflower blossom head again in a few days. When the head turns yellow, cover it with a large paper bag. This will keep birds and squirrels from stealing your harvest before it is ready.
Remove the bag every day to check the blossom head color. When the head turns brown, cut the blossom from the stalk. Leave a foot or two of stalk on, connected to the bloom.
Lay sunflowers on a flat surface in a dry, protected area. A workshop or garage away from rodents would work well. Leave the sunflower heads to dry out.
Rub the flat of your hand against the bloom of the dried flower. This will loosen and remove the seeds. Do this over a counter or table.
Collect the seeds together. Put the seeds into a lunch paper bag. Fold the top of the bag over.
Store the bag in a dry, dark place.
Mark the bag with a pen or marker naming the type of sunflower seed you are storing.