(Based on my wife's experience (administrative ceremony in the Dallas convention center) and mine (judicial ceremony in the Plano convention center), ...)
Don't show up early (of course, don't show up late either). If you show up on time, you'll stand in line just like the folks who show up early.
When you show up you will get directed to a line (and your guests will be directed to the guest section). You will stand in line for 15 to 45 minutes. They'll look at your oath letter, check that you are on the list, and that everything is OK. I'm not sure what happens if you check "yes" to any of the questions on the back of the oath letter.
Then you'll get shown to a seat. At my wife's ceremony, they were seating folks by section (which made handing out the natz certs at the end easier/faster). At mine, they were just seating people in the order they showed up in the room (making sure no empty seats were left).
Once everyone is seated, they then said "well, everyone's here, let's take a break". In my wife's case, it was nearly an hour after the "start time" and we had a 1/2 hour break. I think my break was longer.
Then they start the ceremony. A speech, a "patriotic" video including a "welcome to the USA" message recorded by the president. Then one of the pledge of alligiance or the Star Spangled Banner (the other was after the oath).
Finally, you raise your right hand and read off the oath in chorus with everyone else.
Then the other of the pledge or the anthem and "Congratulations".
At my wife's ceremony, they handed the certs out by section. At mine I had to stand in a 20-30 minute line. You give them your green card, they give you the certificate.
Count on probably spending 2 hours there, even though the ceremony probably lasts about 20 minutes. It's the last chance the USCIS has to waste your time.
Good luck.