How do I start PowerShell from Windows Explorer?

In Windows Explorer, just go to the Address Bar at the top (keyboard shortcuts: Alt+D or Ctrl+L) and type powershell or powershell_ise and press Enter. A PowerShell command window opens with the current directory.

Just to add in the reverse as a trick, at a PowerShell prompt you can do:

ii .

or

start .

to open a Windows Explorer window in your current directory.