  Large surveys with new-generation high-contrast imaging instruments are
needed to derive the frequency and properties of exoplanet populations with
separations from $\sim$5 to 300 AU. A careful assessment of the stellar
properties is crucial for a proper understanding of when, where, and how
frequently planets form, and how they evolve. The sensitivity of detection
limits to stellar age makes this a key parameter for direct imaging surveys. We
describe the SpHere INfrared survey for Exoplanets (SHINE), the largest direct
imaging planet-search campaign initiated at the VLT in 2015 in the context of
the SPHERE Guaranteed Time Observations of the SPHERE consortium. In this first
paper we present the selection and the properties of the complete sample of
stars surveyed with SHINE, focusing on the targets observed during the first
phase of the survey (from February 2015 to February 2017). This early sample
composed of 150 stars is used to perform a preliminary statistical analysis of
the SHINE data, deferred to two companion papers presenting the survey
performance, main discoveries, and the preliminary statistical constraints set
by SHINE. Based on a large database collecting the stellar properties of all
young nearby stars in the solar vicinity (including kinematics, membership to
moving groups, isochrones, lithium abundance, rotation, and activity), we
selected the original sample of 800 stars that were ranked in order of priority
according to their sensitivity for planet detection in direct imaging with
SPHERE. The properties of the stars that are part of the early statistical
sample were revisited, including for instance measurements from the GAIA Data
Release 2.
