ShippingMethod reference
This article provides reference material about ShippingMethod class.
ShippingMethod class represents an information about shipping method.
Properties

Id
Gets Guid identifier of shipping method. This value must be copied to ShippingMethodId property value of ShippingRate class when extension returns shipping costs for the shipping method.
Settings
Gets shipping method settings. You should cast it to your own settings type which is inherited from ShippingMethodSettings when using them.
public override IList<ShippingCost> CalculateShippingRates(ShippingContext shippingContext)
{
    foreach (var method in shippingContext.Methods)
    {
      // getting your custom settings
        var methodSettings = (CustomShippingMethodSettings)method.Settings;
    }
}