Most useful Desired State Configuraiton debugging commands

Okay, here they are:

Get-ScheduledTask "Consistency" | Start-ScheduledTask

This will immediately re-process a configuration.

My scenario is this:
I place my configuration on a pull server.
I then configure the DSC Local Configuration Manager with the GUID of that configuration.

Then I can tweak the configuration and play with it, and not have to push it each time.
Running the consistency command allows me to 'do it now' and force a configuration to be applied, instead of waiting for my configured application window of time to pass.

Trace-xDscOperation | where { $_.EventType -eq "error" } | fl

This requires that you have the xDscDiagnostics module on your target machine. (Which if you are sorting out using DSC and applying configurations - this is necessary).
Lots of folks have blogged about it.
And it is handy with only two commands Get-xDscOperation and Trace-xDscOperation and the value add that it will enable tracing for you the first time you run in. Usability is high in this one.

Get-xDscOperation shows the job list.

Get-xDscOperation

This error you will always see the first time you apply a configuration.

If you want to know if DSC is chugging along and doing its thing you have to check the status of the consistency job:

Get-ScheduledTask "Consistency"

TaskPath                                       TaskName    State
--------                                       --------    -----
\Microsoft\Windows\Desired State Configurat... Consistency Running

Now, lets look at another failure to see the details.

Trace-xDscOperation | where { $_.EventType -eq "error" } | fl

There is good detail in here, you just have to find it.

[Script]MediaDownload is one of my configuration items. It is the Script Resource Provider (that is necessary context for the next)

The detail of the error is actually: MSFT_ScriptResource failed to execute Set-TargetResource functionality with error message: Exception calling "DownloadFile" with "2" argument(s): "The remote server returned an error: (404) Not Found." .

This tells me that the file I am attempting to download is missing (or my URI is wrong).

Another useful case for Trace-xDscConfiguration is right after you apply a configuration using Set-DscLocalConfigurationManager.

When I do this I frequently find a comment that the task will be created pending a reboot.  This indicates to me that DSC is going to do absolutely nothing until I reboot that machine.

I thought I was going insane the first time nothing happened and I stumbled on this message - you don't see it if you use the -Verbose switch, only in the trace.