Like for any other macro you want to insert in AUCTeX, you should use C-c RET
cite RET (or C-c C-m
cite RET; for more information about autocompletion in AUCTeX see the quick start or Completion section of the manual). This works also for all other citation macros provided by
biblatex, ect... (
For the particular case of bibliography commands, you may want to take advantage of the great package RefTeX. AUCTeX has a basic support for bibliographic commands also without RefTeX, but this package provides a far superior completion.
In order to automatically start RefTeX when you open a LaTeX file add the following code to your init file
;; Turn on RefTeX in AUCTeX
(add-hook 'LaTeX-mode-hook 'turn-on-reftex)
;; Activate nice interface between RefTeX and AUCTeX
(setq reftex-plug-into-AUCTeX t)
In this way, you can still insert a
\cite command with C-c RET
cite RET, but you can also use the key-binding C-c [. RefTeX overtakes the task to provide completion of bibliographic entries, but you can continue using the usual AUCTeX-way to insert macros.