I have always germinated them in small flower pots with basic plant soil with perlite. Fresh seeds sprout way faster and generally as a group, stored ones sprout very slow and u get ones that sprout 8+ months later, ive had poor germination from stored ones also. I sprout them at room temperature, around 20C.
They are generally very easy to sprout, last winter i sprouted around 100 seeds, most i tinned, the rest ( 60 or so) were stransplanted in small plastic cups and are now in my basement for the winter with the citrus.