Yellow flags get a lot of attention, but they're a small part of the job description for NFL officials. (AP)

Before we go under the hood to review an NFL official’s day planner, here are some basics:

How much do NFL officials work during the season?

A conservative estimate is 20-25 hours week – not including travel. For head referees 30-35 hours. But there’s always another game to watch or another page in the rule book worth re-reading.

How much do NFL refs earn?

Last season rookies made more than $75,000. The most senior refs just under $200,000.

Bill Carollo retired in 2009 after 20 years as an NFL official, most of them as a head referee. Today the 60-year-old Wisconsin resident manages the officials in four Division-I college football conferences. I asked Carollo to walk me through a referee’s week, starting at the end of a Sunday afternoon game.

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"We would actually go back to the hotel, have food brought in and look at the TV tape of it," Carollo said. "We won’t get the coaches’ tape, which is the sideline and end zone shots they use to evaluate the players. We won’t get that until the next day. So there will be a brief review of all the penalties, any controversial plays."

And like many jobs, there’s paperwork.

"As a referee I have to send in multiple reports to the league about the fouls, about anything that happened on the sideline or anything unusual in the game."

Monday

NFL officials are flying home … or to wherever their other jobs take them. The vast majority of the 119 NFL officials have second careers. Many own businesses or hold senior management positions, but Carollo says tough economic times in recent years have led to bosses asking questions about the amount of time the NFL requires.

“Why don’t you work Fridays and Saturdays? Or why aren’t you working Mondays because you’ve got Monday Night Football?’ And now they’re playing Thursday night football," Carollo said. "It becomes increasingly more difficult, so a lot of the guys are trying to do just officiating."

On Mondays head refs also have a conference call with the front office. For most of his NFL career, Carollo was also an international account executive for IBM – a job that required regular travel to Europe, South America and Asia.

“So a lot of times I would work a ballgame, fly to Beijing. And then phone would ring, “I’m looking for you. There was a couple of offsides calls [we'd like to go over]. Where are you?’. I said, ‘I’m checking into my hotel in China.’”

Mid-Week

NFL referees get instant feedback after every call – in the form of boos, cheers and screaming coaches.

They also get plenty of critiques from the league. The officiating in every game is graded by a former ref.

"We’ll get a pretty good report card, if you will. By Tuesday night all of the games in the NFL are graded and on Wednesday morning, they’ll send out a report to you," Carollo said. "I get the report. I go over it with the person that graded it. Then I have a conference call with my crew and go over the game with them."

With the previous game viewed, reviewed and reviewed again, it’s time to prep for Sunday’s match-up.

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"By Tuesday, we’ll get video of the two teams, so I’ll sort through their typical formations, what types of plays they run. Is it 60 percent passing? Or is it 60 percent running? More of a football analysis," Carollo said.

Each week, NFL officials also get a quiz - a written test on the rules of the game.

Friday, Saturday

Friday night or Saturday morning, it’s time to fly out. Refs are required to arrive at least 24 hours before a game. They fly first-class and the league covers all their travel expenses. Once everyone’s in town, the crew meets for several hours, preparing for the next day’s game and reviewing the week’s quiz. Oh, and there’s more homework. A video:

"Every week, maybe 20 or 25 plays that happen throughout the league that could be a good learning experience. If we made a mistake last week, we want everyone to know the mistake. We don’t hide ‘em … internally. Just so if it happens again, we don’t make the same mistake."

Sunday: "The Best Part of the Week"

There’s more pre-game prep on Sunday morning over breakfast, but before long it’s the moment coaches, players, fans and yes, refs have all been waiting for ... game time.

"That’s the best part of the week. Sunday afternoon at kick-off, those three hours, it’s beautiful," Carollo said. "There’s pressure and we’ll screw up calls and we’ll make some mistakes, but solving those problems and sorting through those difficult calls are why we do it," Carollo said. "Just to see how good we really are, so that’s really what we work for … because it’s the hardest thing that most of us have ever tried to do."