Hi Dylan,
If you have the Design Data folders of both 2010 and 2011 on your machine, the best method is to use the Style Library Manager to do this.
You can find this utility in the Tools menu on the Windows Start menu.
If you only have a couple of styles you can also export the styles manually from Inventor 2010 as xml files and import these in 2011.
This can be done by starting the Style Library Editor from within Inventor and hitting the Export/Import buttons.
There is a also presentation on Youtube that goes in great length on how to use Style Library Manager amongst other things
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=13646334&linkID=9242018
Cheers.
Bob Van der Donck
Inventor Product Support Technical Lead
Bob Van der Donck
Principal UX designer DMG group