Things I wouldn't do

gistfile1.cs

public class Customer
{
public string Name { get; set; }
public int LifetimeValue { get; set; }
}

class Program
{
public const int NoDiscountThreshold = 3;
public const int LowDiscountThreshold = 6;
public const int BigDiscountThreshold = 15;


static void Main(string[] args)
{
	var binner = new Dictionary<int, Action<Customer>>();
	var cheapCustomers = new List<Customer>();
	var regularCustomers = new List<Customer>();
	var vipCustomers = new List<Customer>();

	var customers = new List<Customer>
		{
			new Customer {Name="Bob", LifetimeValue=3}, 
			new Customer {Name="Jimmy", LifetimeValue=3}, 
			new Customer {Name="Sue", LifetimeValue=3}, 
			new Customer {Name="Mary", LifetimeValue=6}, 
			new Customer {Name="Sarah", LifetimeValue=28}, 
			new Customer {Name="Bill", LifetimeValue=41}, 
		};

	binner.Add(NoDiscountThreshold, cheapCustomers.Add);
	binner.Add(LowDiscountThreshold, regularCustomers.Add);
	binner.Add(BigDiscountThreshold, vipCustomers.Add);

	customers.ForEach(c => binner[GetDiscountBin(c.LifetimeValue)](c));
}

private static int GetDiscountBin(int lifetimeValue)
{
	if (lifetimeValue >= BigDiscountThreshold) return BigDiscountThreshold;
	if (lifetimeValue >= LowDiscountThreshold) return LowDiscountThreshold;

	return NoDiscountThreshold;
}
}