Yes, you're all invited, but leave jeans at home

It's one thing to throw a party for 10,000 people. It's quite another when there's an open invitation -- and you're not sure who exactly will show up.

But Deval Patrick's official ascent to office tomorrow is expected to be witnessed by thousands on Boston Common, and the inaugural ball is open to anyone with $50 to spend on a ticket.

But with the governor-elect throwing open the doors to the average person, what exactly is the average person supposed to wear to an inaugural gala? And how exactly is the average person expected to behave?

We offer our program guide for those who want to go -- with advice on apparel (black tie is optional for the galas, the invitations say), a few tips on how to comport yourself (stick to small talk on the weather and the Patriots; avoid religion and politics), a people-watching guide (look for James Taylor, Yo-Yo Ma, and John Updike) and some guesses on the weather.

Many firsts will be set.

It's the first outdoor gubernatorial inauguration on record. At more than $1 million, it's the most expensive. And being sworn in will be the state's first black governor, the nation's second. The first, L. Douglas Wilder , who served as Virginia's governor from 1990 to 1994, is to attend.

Tomorrow morning Patrick will attend an invitation-only interfaith service at the Old South Meeting House before being taken to the State House, where he will spend time with his family in the governor's office preparing to deliver the speech he wrote.

The inauguration will begin at noon, with 350 seats for VIPs arranged on a semicircular stage in front of the State House designed to mimic the House chambers where previous governors were sworn into office. Forecasts are predicting a mostly sunny day, with highs near 60 degrees.

There will be a JumboTron positioned near Park and Beacon streets broadcasting images from the stage.

Four former Massachusetts governors are expected -- Michael Dukakis , Paul Cellucci , Jane Swift , and William Weld . Mitt Romney is not on the list.

Romney is expected to transfer several ceremonial items to Patrick, including a pewter key to the governor's office, a gavel, and an original copy of the 1860 General Laws of Massachusetts. But he'll do it tonight, not on the day of the inauguration as is tradition.

After the inauguration, the State House will be open for visitors. Patrick and Lieutenant Governor Timothy P. Murray will stand in a receiving line for two hours, greeting anyone who wants to talk to them.

Visitors will have to pass through metal detectors. Hot chocolate and cookies will be on hand.

Student delegates from high schools across the state have been invited to spend about two hours with the new governor in a town hall meeting. Suggested attire? "Given the historic significance of Inauguration Day, we respectfully request that all delegates dress appropriately but comfortably. Please leave hats and jeans at home!"

The boys should go with khakis and a collared shirt, girls with a dress or a pantsuit, according to fashion experts.

The Brockton High School marching band will close the event.

Following a private dinner at the Museum of Fine Arts (featuring cuisine from various spots in Massachusetts), Patrick will go to the inaugural celebration.

He will wear a black tuxedo, no tails. The invitation for the gala says that black tie is optional. "Optional means that minimally men should be in a suit and tie, preferably black" said Millie Downing , founder of the Etiquette School of New England in Medfield.

Women should have a floor-length dress that is elegant. And if you have a funky outfit you've been waiting to show off, she said, "don't do it tonight." (She's planning to wear a black dress with pearls; her 10- and 11-year-old boys will be in coats and ties.)

Those expected to attend include political dignitaries, musical stars, and everyday residents.

"With social events of this sort, this is not the time you challenge them on their political stance. 'Mayor Menino, what were you thinking?' This is not that time for that," said Cindy Post Senning, of the Emily Post Institute.

Matt Viser can be reached at maviser@globe.com.