Posting this as a public service announcement due to the lack of correct/official information on the web. Beauvais is the airport for the budget airlines Ryanair, Wizzair and BlueAir.
The bus leaves from Porte Maillot (1 metro line) at the edge of the Peripherique (ring highway). Look for the Palais des Congres, a huge convention center with a hotel tower (Hotel Concorde Lafayette). If you are facing the entrance on the roundabout side, the bus picks up at a parking lot across from the left side of the building.
Buses leave continuously once from 5am to 10pm once the vehicle is full but they suggest arriving 3 hours and 15 minutes before your flight. Online ticket sales were suspended in November 2009, so you must buy when you arrive to Porte Maillot. The ride is about 70 minutes without traffic and costs 15 euros (cash only). The price increased from 14 euros on June 9th, 2010. Not cheap for a bus emblazoned with the words “pas cher” on it.
The Ter train leaves from Gare du Nord to the city of Beauvais but you have to take a tax from the train station, making it more time intensive and more expensive. Paris by Train has detailed instructions here. There are also shuttle van services but even with more than 4 passengers, it’s not more cost effective than the bus.
If you only have carry-on you can go directly to the front of the bag check line to get your visa stamp, but be nice and friendly. The 10kg carry-on weight restriction is never measured, just size of the bag. If you’re concerned, go through the security line when the bag size check person is not at the front and you’ll be fine.
Get in touch with the author @untappedmich.