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We have identified several tens of extremely metal-poor star candidates fromSDSS and LAMOST, which we follow-up with the 4.2m WHT telescope to confirmtheir metallicity.We follow a robust two-step methodology. We first analyze theSDSS and LAMOST spectra. A first set of stellar parameters is derived fromthese spectra with the FERRE code, taking advantage of the continuum shape todetermine the atmospheric parameters, in particular, the effective temperature.Second, we select interesting targets for follow-up observations, some of themwith very low-quality SDSS or LAMOST data. We then obtain and analyzehigher-quality medium-resolution spectra obtained with ISIS on the WHTtelescope to arrive at a second, more reliable, set of atmospheric parameters.This allows us to derive, with accuracy, the metallicity, and confirm theextremely metal-poor nature in most cases. In this second step we also employFERRE, but we take a running mean to normalize both the observed and thesynthetic spectra, and therefore the final parameters do not rely on having anaccurate flux calibration or continuum placement. In order to verify ourresults we have analyzed with the same tools, and following the same procedure,six well-known metal-poor stars, five of them at [Fe/H]<-4, showing that ourmethodology is able to get accurate metallicity determinations down to[Fe/H]<-5.0. The results for these six reference stars give us confidence onthe metallicity scale for the rest of the sample. In addition, we present 12new extremely metal-poor candidates: two stars at [Fe/H]=-4, six more in therange -4<[Fe/H]<-3.5, and four more at -3.5<[Fe/H]<-3.0.

WHT follow-up observations of extremely metal-poor stars identified from SDSS and LAMOST