Put ads up everywhere you think actors will be. Flyers in theatres, schools, a post on kijiji/craigslist etc.
Let responses trickle or flood in for about 2 weeks more or less, depending on if you get the right actors and are satisfied with your decision.
Send out the lines you want read to those that respond, making sure people know the bios of the characters and their motivations for their scenes etc.
Hold auditions in a place that is accessible to the majority of people in your city. Libraries, schools, community halls, anywhere with meeting rooms pretty much.
Bring a camera with you and just let it roll all day if you can, then just time stamp everyones resume/headshot so you know who is who because you will probably forget who you really liked by the end of the day.
Do it at reasonable hours. Trying to get both people that work at night and people who work during the day is tough, renting a room for the entire day or two should do it.
Have someone greet every potential actor and direct them to the waiting area or audition room. And if you can, try and get 1 male 1 female in the audition room at all times to make everyone comfortable. Have water/coffee/snacks if you think there will be a long lineup for most of the time.
Try and limit everyones audition time to about the same every time. Holding an actor for an extra 5 minutes to chat or try other lines will make other people annoyed.
Call back everyone who auditioned and let them know if they got it or not.
