Get your individual design exactly how you want it.
If you know you will be rotating the full board to fit multiple copies onto the panel then make sure you set the 'Spin' property of any text, name and value items.
Save a copy of the .brd as *-to_panelise.brd
Open the *-tp_panalise.brd file.
Set all layers to visible.
Run panelize.ulp - this copies some layers, such as tNames and bNames to new layers, the numbers incremented by 100. i.e. 25 tNames to 125_tNames
Save the file
Do a group select of the whole board, still with all layers selected.
Select Copy from the file menu
Close the file
Create a new blank .brd file from within Eagle Control Panel
Select Paste from the file menu and paste copies of your board in as required, rotating to fit. If you have done it right then the text should all stay in the correct orientation.
Once done create an overall board outline in the 46 - Milling layer. Multiple Dimension outlines can cause issue when you output the board to a 3D renderer or Gerbers. Any copper fills also run to Dimension layers so this will preserve correct copper fill distances on individual sub boards.
Mark out any cut lines on the panel in a suitable layer, such as tPlace. I normally leave 4mm between sub boards.
When outputting the panel to print, Gerbers or 3D renderer then be sure to select the correct layers. Don't use 25 & 26 for Names, use the copied layers 125 & 126. Use 46 - Milling for overall board outline.
I've typed this quickly as I need to go out, but hopefully not forgotten anything.