Just a simple quick tips for all you guys out there. A couple of students have come back and asked me – “How did you enable that really nice dashbord”. It’s simple, easy and safe.

If you think the below is to much, then check out Wiktor Wiléns blog for a nice farm scoped feature moving this into the gui (and some other stuff also)
http://www.wictorwilen.se/Post/SharePoint-2010-Developer-Dashboard-configuration-feature.aspx

Anyways, here you go:

Via STSADM: stsadm -o setproperty -pn developer-dashboard -pv OnDemand 
Via PowerShell: (Get-SPFarm).PerformanceMonitor.DeveloperDashboardLevel = “OnDemand”

The value OnDemand can also be On or Off (On=Always shown, OnDemand=Shown of request, Off=Never shown)