How do I generate a tnsnames.ora file to connect to an Oracle Database?
You can easily create a tnsnames.ora [text] file.  It should be in $ORACLE_HOME/network/admin/ and should look something like this:

 ORATST=
 (description=
   (address_list=
     (address = (protocol = TCP)(host = fu.bar)(port = 1521))
   )
 (connect_data =
   (service_name=oratst)
 )
)