The Standard Model of particle physics currently stands as our most complete theory of fundamental particles and interactions. It is a well tested physics theory but tensions have been found between theoretical predictions and experimental results. These discrepancies can be either a sign of New Physics or the result of insufficient control over theoretical and experimental uncertainties. In order to detect/rule-out new physics effects in the flavour sector it is important to improve our understanding of flavour changing processes which occur at tree and loop level in the Standard Model. Semileptonic B decays provide promising channels to test the Standard Model and search for signs of New Physics. While the B-factories and LHCb carry out measurements of B-meson observables, theoretical determinations of form factors are necessary for the extraction of Cabibbo-Kobayashi-Maskawa matrix elements, the determination of differential branching fractions and angular distributions amongst other quantities. In this work we present the calculation of Bs → Klv, Bs → Dslv and Bs → øl+l- form factors using the Columbia interpretation of the relativistic heavy quark action for the b-quark and the domain wall fermion action for light, charm and strange quarks. In conjunction with future experimental data, our form factor results for Bs → Klv and Bs → Dslv decays will provide a new method to extract the CKM matrix elements ΙVubΙ and ΙVcbΙ, test the forward backward asymmetry and measure the ratios R(K) and R(Ds). Similarly, Bs → øl+l- form factors will allow for the reconstruction of many observables that offer important tests of the Standard Model and New Physics scenarios.