[Asherweef]

Love how everyone does it differently. None of it sounds as messy as me though 

[JayG]

For seeds big enough to see and handle, I fill tray with compost, firm down with palm of hand, select appropriate digit for size/depth of seed, and poke holes in compost. Drop one seed in per hole, ruffle surface to fill holes in, water, label.

Same technique using 'built in' digital depth guide for larger seeds, but they are usually in small pots (paper or plastic as appropriate.)