The following configuration, by ksakai@mtl.t.u-tokyo.ac.jp, should work. Some lines may be omitted according to your configuration. The last three lines may be changed according to your taste. (See the documents of Supercite for detail.)
;; sc
(autoload 'sc-cite-original "supercite" "Supercite 3.1" t)
(autoload 'sc-submit-bug-report "supercite" "Supercite 3.1" t)
(autoload 'sc-perform-overloads "sc-oloads" "Supercite 3.1" t)
(setq mail-citation-hook 'sc-cite-original)
(setq mail-yank-hooks 'sc-cite-original) ; for all but MH-E
(setq mh-yank-hooks 'sc-cite-original) ; for MH-E (3.7以Γ恐糸)
(setq news-reply-mode-hook 'sc-perform-overloads) ; for RNEWS,GNEWS,GNUS
(setq mail-setup-hook 'sc-perform-overloads) ; for RMAIL,PCMAIL,GNUS!
(setq gnews-ready-hook 'sc-perform-overloads) ; for GNEWS
(setq sc-electric-references-p nil)
(setq sc-preferred-header-style 1)
(setq sc-citation-leader "")