Start counting a week after seeding and repeat a couple of times over the following two weeks.
Sample a few random areas in the field to get a feel for establishment. Try different topographies and refer to field notes to make a connection, if any, between seed survival and field conditions at and after seeding.
With the first count, mark a few specific spots, count and record emerged plants within those areas, and then revisit that same area a few days later to recount.