I believe they take the players age, international caps, current form, experience, disciplinary record, goals record, speed, height, work-rate, and popularity with the fans into consideration, then discuss what the player himself and his manager believe his worth to be.
Then the directors come up with a laughably low weekly wage and haggle with the kid whilst setting unreasonable deadlines for him to make a decision.
Then the player signs for Plymouth and we all forget about him, until he gets homesick and moves to Partick Thistle.