Preoperative assessment is an elementary step before approaching surgery. All formerly described anatomical and pathophysiological elements need to be considered in order to choose the most adequate and tailored surgical approach. Clinical examination is the simplest method to obtain a first impression of tumor extension. Radiological imaging is important not only for staging but also for strict evaluation of the muscles and other tongue structures that enclose the oncological compartment to remove surgically. For this reason, MRI is preferred for its contrast and resolution. On the other hand, CT is complementary for local mandible bone invasion evaluation (if clinically suspected) and chest distant metastasis assessment. Ultimately, biopsy is elementary in order to confirm histologically the presence and the type of a malignant tumor. This chapter encloses detailed information about each preoperative workup for accurate tumor staging. The chapter ends with a practical enlightenment of how all findings lead to a tailored surgical planning.