  This article focuses on certain variability and emission characteristics of
Active Galactic Nuclei (AGN), especially their radio-loud subset consisting of
quasars, BL Lacs and $\gamma$-ray detected narrow-line Seyfert 1 galaxies, all
of which exhibit relativistically beamed jets of nonthermal radiation. Several
striking trends and correlations, including some that have received scant
attention, drawn from the available comparatively recent literature are
highlighted. These can provide very useful inputs to models of AGN and be
probed at a deeper level using the optical telescopes recently set up at
Devasthal (Nainital).
