  We present the first results of a ground-based programme conducted on 1-4m
class telescopes. Our sample consists of 1097 active and presumably young
stars, all of them being optical counterparts of RASS X-ray sources in the
northern hemisphere. We concentrate on the 704 optically brightest
(V_Ticho<=9.5 mag) candidates. We acquired high-res spectroscopy in the
Halpha/Li spectral regions for 426 of such stars without relevant literature
data. We describe the sample and the observations and we start to discuss its
physical properties. We used a cross-correlation technique and other tools to
derive accurate radial/rotational velocities and to perform a spectral
classification for both single and SB2 stars. The spectral subtraction
technique was used to derive chromospheric activity levels and Li abundances.
We estimated the fraction of young single stars and multiple systems in stellar
soft X-ray surveys and the contamination by more evolved systems, like RS
CVn's. We classified stars on the basis of Li abundance and give a glimpse of
their sky distribution. The sample appears to be a mixture of young
Pleiades-/Hyades- like stars plus an older Li-poor population (~1-2 Gyr). 7
stars with Li abundance compatible with the age of IC 2602 (~30 Myr) or younger
were detected as well, although 2 appear to be Li-rich giants. The discovery of
a large number of Li-rich giants is another outcome of this survey. The
contamination of soft X-ray surveys by old systems in which the activity level
is enhanced by tidal synchronisation is not negligible, especially for K-type
stars. 5 stars with Li content close to the primordial abundance are probably
associated with known moving groups in the solar neighbourhood. Some of them
are PTTS candidates according to their positions in the HR diagram.
