A version of this recipe was recently in the New York Times. I've been making it this way for years and it's so much better than the recipes which start with hot brewed coffee. I usually start this at night to have fresh iced coffee the next day.
In a jar with a tight fitting lid combine coffee grounds and 4 1/2 cups cold water. Cover and shake well. Set aside at room temperature at least 12 hours.
Strain the coffee twice through sieve lined with a coffee filter or cheesecloth. Pour the strained coffee into a large pitcher. Add the remaining 4 1/2 cups cold water. Serve with sweetened condensed milk or sugar and regular milk.
Note: Make one batch to use for ice cubes. Freeze the coffee in ice cube trays and serve iced coffee with frozen coffee cubes so it doesn't get watered down.