The parade on the first day is just with the tent owners, the waitresses and the fancy beer wagons drawn by 6 - 8 horses got up regardless in silver and bells and prancing like thoroughbreds although they're coldbloods. It's pretty but not spectacular.
Don't miss the parade on the second day, that's the one with costumes from all over Europe, Bavarian brass bands, live eagles, crafts such as lace making or harvest labor such as threshing being performed on floats and politicians in flowered horse-drawn carriages.
Things that happen on opening day:
Lord Mayor Ude taps the keg by sheer will-power alone but pretends to hit the tap 1.5 times.
The U-Bahn trains are held back because the platforms at the main stop are crowded with people waiting to exit the station,
Theresienwiese. Get off at Schwanthalerhöhe or
Goetheplatz instead.
The first falling down drunk guy is picked up at app. 2.17pm and brought to the Red Cross station on a covered trolley.
The knoll behind the tents is littered with people sleeping it off or getting it on.
People will gather outside the tents at the crack of dawn ready to rush in and grab tables as soon as the doors open at 9am (IIRC).