Answer: Once the fully mature seed heads are harvested and dried, shake them to free the seeds. If you have alot of them you can make a screen to shake the seeds through while trapping the stems and other debris. The only other preparation would be to rub them in your hands to remove the little spines on the seeds, but that is optional.
Carrot seed usually germinates at a wide soil temperature range but the highest rate would be at about 77 degrees; it can take one to three weeks depending on the soil temperature and the moisture available. You might have a problem if they are allowed to dry out or if the soil surface is allowed to crust at all. Also, if you saved seed from a hybrid it is possible the seed is not viable. Your storage conditions may also have affected the viability.
To check viability you might try presprouting on a damp paper towel enclosed in a plastic bag and kept in a bright spot (but out of direct sunlight).
Q&A Library Searching Tips