SPContext.Current.FormContext
I'm always forgetting this simple but very useful line so here it is :)
FormContext has this very cool Method SetFormMode and also this two properties FieldControlCollection (Get a collection of the Field Controls) , FormMode (Get the Current SPControlMode)
SPControlMode - http://msdn2.microsoft.com/en-us/library/microsoft.sharepoint.webcontrols.spcontrolmode.aspx
When you navigate to a page, and “Edit” the page, the page "mode" is changed and you are presented with data entry controls that let you enter data into page fields.
So a Page can be in different modes, SPControlMode enumeration contains these values (Display, Edit, Invalid and New)