Usually there is a set theme, and you get points for adhering to it.

The last round featured the Thieves Guild, and you received points for each quest completed, and a bonus for completing them all. Plus other points and bonuses for radiant questing, and stone hunting.
Typically we have a multiplier in place for the different difficulty levels that help determine the winner, IE;
Novice .50
Apprentice .75
Adept 1.0
Expert 1.25
Master 1.50
Legendary 1.75
On some rounds we also do randomly drawn skills. For instance, in the TG round; Conjuration, Illusion, Destruction, Light armor, and Archery were the drawn skills, and the only ones you could level/perk. Speech, lockpicking, and sneak are usually given as freebies, since it's impossible to not raise those. But if you raise other skills not chosen, you get docked points.
For round 5, though, you get to pick your class/build and relevant skills, and will only be allowed to level and perk those that are chosen. But, the freebie skills will likely be the same.