UILabel *myLabel = [[UILabel alloc] init];
myLabel.text = @"There are three types of people in this world: those who make things happen, those who watch things happen, and those who wonder what happened. Which do you want to be?";
myLabel.numberOfLines = 0;

CGSize maxLabelSize = CGSizeMake(self.view.frame.size.width - 32.0f, FLT_MAX);
CGSize expectedLabelSize = [myLabel sizeThatFits:maxLabelSize];

myLabel.frame = CGRectMake(16.0f, 16.0f, expectedLabelSize.width, expectedLabelSize.height);