As a baseball history buff, for a long time my way of “counting sheep” in bed was:
5 baseball players whose last name begins with the letter “A”,
then “B”, “C”, etc.

When after a few nights I worked my way up to “Z”, I started over, but with a twist:
5 baseball players, whose last name begins with the letter “A”, and who played before 1950.

Then when I made it to “Z”,
5 baseball players, whose last name begins with the letter “A”, and who played after 1950.