The service name is an alias in the tnsnames.ora on the server.
You are not putting < and > , right? :)
And the select would be
create database link some_db_link_name connect to some_user_name identified by the_password_of_some using 'some_alias_in_tnsnames';
select * from some_remote_table@some_db_link_name;
1)try to ping and tnsping your remote db to eliminate networking problems. If you get expected responses your network is doing good.
2)try to connect to your remote database using sqlplus.
if it lets you in there are no problems with your tnsnames.ora. That will be another good thing.
If there are problems with two checks above resolve them first. If there are no problems and your db link doesn't work post your error message here and we'll try to help.