Like John B mentions, I have found some need a period of dormancy, others may not, but take a few weeks to sprout. You'll have to experiment until you get to know the requirements of a particular variety.
For the Saramuyo seeds I received from JF, I found that the seeds I planted right away had low germination. Those that I stored for months then planted in the spring pretty much all sprouted, both on heated mats indoors and those left in pots outside.
For me the best medium has been coir for seedlings, it is very finely ground and rinsed of salts with neutral pH. For plants that are sensitive to alkalinity, I hydrate with rain water. After it's hydrated, I squeeze out all the excess moisture, and place into ziplock sandwich bags, leaving room for the sprouts to grow. Place seeds near the top and covered lightly, then seal the bags. As long as the medium has been squeezed of the excess moisture, you should not have a problem with the seeds molding. Sealing the bags keeps the medium from drying out and maintains humidity as the seedlings sprout. I check the bags weekly, once I see the seeds starting to sprout, i open the bag a little bit to allow fresh air and grow in the bag until the first leaves have grown for about a week. The fine coir medium allows me to separate sprouted seedlings easily. These bags are placed on a heating mat indoors and receive late afternoon sun through a window.
Some seeds with a long dormancy period like passion fruit seeds, I plant in pots outside, often in a pot already growing a plant, in a partially shaded spot and they usually sprout on their own in spring after our winter rains. I've had seeds sprout even after a couple years. So I agree with Brian, don't give up on the seeds if they haven't rotted.
It's taken me a lot of trial and error, but the above mentioned strategy has been successful for me. Good luck to you.
Janet
