SpamCop FAQ : SpamCop Blocking List information : How do I configure my mailserver to reject mail based on the blocklist? :
Here is a sample of one user's (thanks Ian) main.cf where the SCBL is used:

maps_rbl_domains = bl.spamcop.net

smtpd_recipient_restrictions =

reject_invalid_hostname,

reject_non_fqdn_sender,

reject_non_fqdn_recipient,

reject_unknown_sender_domain,

reject_unknown_recipient_domain,

reject_unauth_pipelining,

permit_mynetworks,

reject_unauth_destination,

reject_maps_rbl,

permit

Another example using several BL's is available at http://jimsun.linxnet.com/misc/postfix-anti-UCE.txt