Flying directly into Montreal is the easiest way to go, and we have information about it at: www.library.mcgill.ca/iaml2012/node/12. But if you are concerned about costs and need a cheaper option-- flying to Burlington, Vermont is possible and sometimes from the U.S. it can be half the price. You just need to be prepared for a bus trip from there, which happens several times per day. For the airport you can see which airlines fly to Burlington: http://www.burlingtonintlairport.com/ Here's the schedule of the bus from Burlington to Montreal: http://www.burlingtonintlairport.com/Greyhoundschedule.htm
My sister flew into Burlington a year ago to visit me in Montreal and she saved $400 on the flight and it was a nice trip in northern Vermont to Montreal. We did that part by car and visited Burlington for lunch on the way back to the airport, which made a nice side trip.
Also, knowing the Amtrak has inexpensive service from New York City. See the other post about that option, but know it is much farther, but might work for a pre or post conference trip. http://www.amtrak.com/servlet/ContentServer?c=AM_Route_C&pagename=am%2FL...