With the large energies reached at the LHC, massive particles like the W, top or Higgs will often be produced heavily boosted. When they decay hadronically, their decay products will therefore often appear as a single jet. In this talk, I shall give an overview of the basic techniques, based on studying the properties of subjets, that people have recently developed to help tagging those boosted objects efficiently. As a particular example, I shall discuss in more details the case of ttH final states.