Studying cosmology with large galaxy surveys requires an unprecedented understanding and mitigation of systematics -- a challenge that can be addressed on two fronts: quantification of the impacts of systematics, and new tools to mitigate them. Addressing the first, I will discuss work on the artifacts induced by the observing strategy for the Large Synoptic Survey Telescope (LSST) and present large dithers as an effective mechanism to mitigate the induced artifacts (Awan et al. 2016, ApJ, 829, 50) -- a result that has now been adopted for the baseline LSST observing strategy. I will also discuss the impacts of Milky Way dust on large-scale structure studies and our efforts to mitigate them. As for new tools, I will present new galaxy angular correlation function estimators that explicitly correct for sample contamination arising from photometric redshift estimation (Awan & Gawiser, 2019, submitted to ApJ; arXiv 1911.07832); our weighted estimator can be optimized to improve the precision of cosmological parameter estimation. While these techniques are motivated by preparations for LSST, they are applicable to DES, DESI, HETDEX, Euclid, and WFIRST.