Festivals:
Oktoberfest: The first Oktoberfest took place on the 12 October 1810, to celebrate the marriage of Prince Ludwig of Bavaria and Princess Therese of Sachsen-Hildburghausen. All citizens of Munich were invited to a meadow (Wies'n) situated in front of the city tower, subsequently renamed the Theresienwiese in honor of the bride. In the early years of the fair, horse races were held, then as the event grew, included agricultural conventions, which still take place every third year. In 1896, businessmen working with the breweries in Munich built the first giant beer tents at Oktoberfest, and drinking has been the primary focus since. Each of the major breweries presides over its own large tent filled with traditional musicians leading the crowd in well-known drinking chants, incredibly strong barmaids hoisting ten or more huge Maß (1-liter glass beer mugs that are heavy even when empty!), and a spate of drunken people all trying to get into the bathroom at once. In 2003, Oktoberfest hosted 6.4 million visitors who drank 6.1 million liters of beer and ate the equivalent of 91 oxen, 383,000 sausages and 630,000 chickens. However, visiting the Oktoberfest can be much more stressful than the visit of similar festivals (Cannstatter Wasen, Wurstmarkt Bad Dürkheim, etc.), because the tents are overcrowded and there are doormen at the entrance ruling the procedure of coming in. Especially at weekends you should try to get in the tents before 10AM. During the week, most tents are open all day, however it is not easy to get a seat and as a general rule, you won't get served if you haven't got a seat. It is not recommended to leave the tent if you want to get in it later the day. So you have to decide early in the morning if you want to go in a certain tent or you want to enjoy the rides like the coaster with 5 loops. Some tents, such as the Hofbräu Festzelt have a standing area that do not require seating; as such, you can sometimes get into this tent later than with other ones. If the weather is nice, you can enjoy your beer any time at the open air tables besides the beer tents. You won't experience the typical beer tent atmosphere with Bavarian oompah music though. An alternative is "Das Wiesnzelt am Stiglmaierplatz". The historic Löwenbräukeller is about 2km away from the Oktoberfest and offers Wiesn-atmosphere without the usual closing time, all other tents are bound.
Maibaumaufstellung: On the 1st of May (which is a public holiday in Germany) strange things happen in some Upper Bavarian villages and even in Munich... Men in Lederhosn and girls in Dirndln carrying long poles meet on the central square. With these poles an even longer white-blue pole is erected. There is usually an oompah band playing, booths selling food and drinks and tables where you can sit down and enjoy this non-touristy spectacle. The large white-blue pole you find in almost every village and dozens in Munich (e.g. on the Viktualienmarkt) is called Maibaum (meaning may tree - known in English as a maypole) and the villages compete who has the tallest and the straightest one. It is cut down every three to five years and re-erected in the following year. Ask a local which village or district of Munich does it this year and be there not later than 10AM. There's several traditions revolving around maypoles, like the dance of the unmarried men and women. The weeks before May 1st, each village has to guard its maypole, because if some other village manages to steal it, they'll have to buy it back. Usually with beer...
Tollwood: In summer in the Olympic park, in winter on Theresienwiese (Oktoberfest area), these 3-week festivals combine ethnic food, souvenir shops, concerts and theater, and they are very popular among the locals.
Christkindlmarkt / Christkindltram: see extra section below.
Theater, Opera, and Music:
Residenztheater: Variety of classical and modern plays.
Nationaltheater: Shows ballet and opera performances almost every night. The Bavarian National Opera Company is said by critics to be one of the best in the world!
Staatstheater am Gärtnerplatz: Smaller than the National Theater, this is a very good alternative for interesting productions of operas, operettas and musicals. Tickets are generally still available on short notice, even when the big opera houses have been sold out for weeks.
Deutsches Theater: More musicals and theme shows (like MAMA MIA!, etc).
Kammerspiele: which often surprises viewers with very modern (and sometimes shocking) interpretations of famous plays.
Volkstheater: is somewhere between Bavarian Folklore and modern theater.