http://example.com/wiki/Pages/home.aspx?ControlMode=Edit&DisplayMode=Design
http://example.com/wiki/Pages/home.aspx?ControlMode=Edit&DisplayMode=Design
You need to pass the parameter ControlMode=Edit and DisplayMode=Design to the aspx page if you like to open it in edit mode.
It's the same as it always was. SharePoint 2010 just hides the parameter and change the modes using a Javascript.