  The main purpose of this work is to improve the existing knowledge about the
most powerful engines in the Universe - quasars. Although a lot is already
known, we still have only a vague idea how these engines work exactly, why they
behave as they do, and what the relation is between their evolution and the
evolution of their harboring galaxy.
  Methods we used are based on optical spectroscopy of visually bright quasars,
many of which have recently been discovered as X-ray sources, but eventually
missed in color-selected surveys. The spectra typically cover the 4200-7000 AA
region, allowing measurements of the characteristics of the hydrogen lines, the
FeII contribution, and other lines of interest.
  We present accurate redshift estimates and Seyfert type classification of the
objects. We also show that the contribution of the host galaxy to the optical
continuum is non-negligible in many cases, as is the intrinsic AGN absorption.
Consequences of not correcting for those factors when estimating different
quasar parameters are discussed. We also find some evidence of a non-unity
slope in the relation between the internal extinction based on the Balmer
decrement and the one on the optical continuum slope, implying, if further
confirmed, the intriguing possibility that some absorbing material might
actually be located between the continuum source and the broad-line region.
