Using PowerShell to find the GUID of an SPField instance

In SharePoint, I occasionally need to find the GUID of a field in a custom list. The following PowerShell will spit out the field's GUID:


$web=get-spweb https://mysite.com/mysite/
$list=$web.lists["My List Display Name"]
$list.fields["MyFieldName"].id

Using PowerShell to downgrade a SharePoint v4 site to v3

Use the following powershell commands on a SharePoint front end server to downgrade a v4 site to v3.

$Web=Get-SPWeb http://<site name>/<site>

$Web.UIVersion=3

$Web.UIVersionConfigurationEnabled=$true

$Web.update()