A few data-driven methods used in deriving the normalization of the dominant top quark background contribution in the $ H → WW(*) → {\ellν\ellν}$ analyses by the ATLAS and CMS experiments at the LHC are reviewed and compared. Additional information, justi fication or modi fication to some of the methods is provided. These methods have also been or can be applied to other analyses such as cross section measurements of the Standard Model WW process and searches for new physics in channels with similar final states.