An extremely useful tool that converts any WCF binding to a custom binding: WCF Binding Box. Why? Sometimes it is easiest to start from a simple pre-defined binding and then modify it to do your thing. (this is also a good way of learning what goes into the predefined bindings – for example: its clear below that the BasicHttpBinding implments Soap version 1.1)
Here is an example of converting a BasicHttpBinding to a custom binding.
<!-- generated via Yaron Naveh's http://webservices20.blogspot.com/ --> <customBinding>
<textMessageEncoding MessageVersion="Soap11" />