If you're flying into Minneapolis/St. Paul International Airport, the easiest and cheapest way to get to downtown Minneapolis is via the light rail. You can board from either the Humphrey or Lindbergh terminals* (depending on which airline you arrive on) and you'll go to the Downtown East/Metrodome Station stop.
One way rail fares are $2 during rush hours and $1.50 at all other times.
Rush hour fares apply Monday through Friday (except holidays) from 6 AM to 9 AM and from 3 PM to 6:30 PM. Trains do not run from about 1 AM to 4 AM in the morning.
There are no fare boxes on trains. You pay for a ride before boarding the train.
On the map below, Point A represents the Downtown East/Metrodome light rail station. It's within walking distance of Open Book, where the conference will be held, and the Holiday Inn.
* The Lindbergh and Humphrey terminals are in the process of being renamed Terminal 1 and Terminal 2 respectively.