Stored Procs, Error Handling And Return Values

Can anyone let me know the prefered method for handling stored procedure errors. 
I usually trap the error in the stored proc and then return a value using an output parameter

e.g stored proc

if @@error <> 0 begin
set @returnValue = -1
return
end

c#com.Parameters.Add("@returnValue", SqlDbType.Int).Direction = ParameterDirection.Output;
con.Open();
com.ExecuteNonQuery();

int result = (int)com.Parameters[0].Value;

if (result == -1)
{
//throw exception
}
else
{
//do whatever
}