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Using a spectroscopically confirmed sample of M-giants, M-dwarfs and quasarsfrom the LAMOST survey, we assess how well WISE $\&$ 2MASS color-cuts can beused to select M-giant stars. The WISE bands are very efficient at separatingM-giants from M-dwarfs and we present a simple classification that can producea clean and relatively complete sample of M-giants. We derive a new photometricrelation to estimate the metallicity for M-giants, calibrated using data fromthe APOGEE survey. We find a strong correlation between the $(W1-W2)$ color and$\rm [M/H]$, where almost all of the scatter is due to photometricuncertainties. We show that previous photometric distance relations, which aremostly based on stellar models, may be biased and devise a new empiricaldistance relation, investigating trends with metallicity and star formationhistory. Given these relations, we investigate the properties of M-giants inthe Sagittarius stream. The offset in the orbital plane between the leading andtrailing tails is reproduced and, by identifying distant M-giants in thedirection of the Galactic anti-center, we confirm that the previously detecteddebris in the outer halo is the apocenter of the trailing tail. We also findtentative evidence supporting an existing overdensity near the leading tail inthe Northern Galactic hemisphere, possibly an extension to the trailing tail(so-called Branch C). We have measured the metallicity distribution along thestream, finding a clear metallicity offset between the leading and trailingtails, in agreement with models for the stream formation. We include an onlinetable of M-giants to facilitate further studies.

Selecting M-giants with infra-red photometry: Distances, metallicities and the Sagittarius stream