Well for large roles I do two casting calls, but I advertise them at least 2 months in advance (That brings about 30 people each casting call).
The first casting call I put out is for "All Types" even though I know I'm really looking for specifics, this is just to create buzz This way word spreads that there's a movie being made and the REAL actors show up to the following casting call.
Usually when writing, I think of places that will most likely be available to me. With this movie, since it's zombies, I knew a lot of it would have to take place outside. But guess what? The world ain't exactly apacolyptic at the moment and I don't have money to block off Main Street so I made most of the story take place out in the woods If it's a house, or restaurant, or office, you can usually ask a friend or a business owner to tape without problem.
Safe Haven took about 20 days to make, but that 20 days was over a span of 4 months. Mostly due to there being a cast of 20 people..... and that's 20 people all with a life and with their own schedules. Which is why I'm cutting down to about 10 people for my next project. The movie honestly could of been shot in 3 weeks if no one had school, work, ect.