  We utilize a complete sample of RR Lyrae stars discovered by the QUEST survey
using light curves to design selection criteria based on SDSS colors. Thanks to
the sensitivity of the u-g color to surface gravity and of g-r color to
effective temperature, and to the small photometric errors (~0.02 mag)
delivered by SDSS, RR Lyrae stars can be efficiently and robustly recognized
even with single-epoch data. In a 100% complete color-selected sample, the
selection efficiency (the fraction of RR Lyrae stars in the candidate sample)
is 6%, and, by adjusting color cuts, it can be increased to 10% with a
completeness of 80%, and to 60% with 28% completeness. Such color selection
produces samples that are sufficiently clean for statistical studies of the
Milky Way's halo substructure, and we utilize it to select 3,643 candidate RR
Lyrae stars from SDSS Data Release 1. We demonstrate that this sample recovers
known clumps of RR Lyrae stars associated with the Sgr dwarf tidal tail, and
Pal 5 globular cluster, and use it to constrain the halo substructure away from
the Sgr dwarf tidal tail. These results suggest that it will be possible to
study the halo substructure out to ~70 kpc from the Galactic Center in the
entire area imaged by the SDSS, and not only in the multiply observed regions.
