Brian's basically right in that if you can tnsping your database, most everything is in place to connect to it. It's worth clarifying, though, that the argument to tnsping is not necessarily a SID. It's actually a resolvable name (an entry in $ORACLE_HOME/network/admin/tnsnames.ora, if you're using local naming and the default location of this file). In my system, the SID and TNS name are the same, but that's coincidence. My document above assumes local naming, but you could very well make the necessary changes (to sqlnet.ora) to use host-based naming, an Oracle Names server, or LDAP as well.
