I find lettuces easy to start in media, indoors then transplant. Had some trouble germinating spinach. I read something about starting them in cold to cool temps. Now I papertowel and baggie sprout spinach in the refrigerator, (about 2 weeks), pot up in media inside for a while, then plant out. I still start 3-4 seeds for every spinach transplant.
This is a link to germination temps as related to days and percentages.YMMV.
http://tomclothier.hort.net/page11.html
Oh yeah, have to use fresh seed, last years does not de well for me.