Enable tracing in WCF

 Put this section anywhere below configSections in web.config

<system.diagnostics>
    <sources>
      <source propagateActivity="true" name="System.ServiceModel" switchValue="Warning, Critical, Warning">
        <listeners>
          <add type="System.Diagnostics.DefaultTraceListener" name="Default">
            <filter type="" />
          </add>
          <add initializeData="trace.svclog"
            type="System.Diagnostics.XmlWriterTraceListener" name="sdt"
            traceOutputOptions="None">
            <filter type="" />
          </add>
        </listeners>
      </source>
      <source name="System.ServiceModel.MessageLogging" switchValue="Warning,ActivityTracing">
        <listeners>
          <add type="System.Diagnostics.DefaultTraceListener" name="Default">
            <filter type="" />
          </add>
          <add name="ServiceModelMessageLoggingListener">
            <filter type="" />
          </add>
        </listeners>
      </source>
    </sources>
    <sharedListeners>
      <add initializeData="web_messages.svclog"
        type="System.Diagnostics.XmlWriterTraceListener, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
        name="ServiceModelMessageLoggingListener" traceOutputOptions="Timestamp">
        <filter type="" />
      </add>
    </sharedListeners>
    <trace autoflush="true" />
  </system.diagnostics>

---------------------------------------------------

Put this under system.ServiceModel section

<system.serviceModel>

 <diagnostics performanceCounters="Default">
      <messageLogging logEntireMessage="true" logKnownPii="true" logMalformedMessages="true"
        logMessagesAtServiceLevel="true" logMessagesAtTransportLevel="true" />
      <endToEndTracing propagateActivity="true" activityTracing="true"
        messageFlowTracing="true" />

 </diagnostics>

</system.serviceModel>