migrate from sql server 2012 to sql server 2008 R2
One way to do this is to use a tool such as Redgate SQL Data Compare. I have had to do this in the past and it has worked well. First you run a schema compare to create an empty database in the 2008 server and then run data compare to pump the data in.

There are other vendors offering similar tools and I believe the new Visual Studio also has something like this. The Redgate offering does give you a two week trial which may be good if you only need it for a one of migration.

Click here for the trial.