  The classical global criteria for the existence of Hamilton cycles only apply
to graphs with large edge density and small diameter. In a series of papers
Asratian and Khachatryan developed local criteria for the existence of Hamilton
cycles in finite connected graphs, which are analogues of the classical global
criteria due to Dirac (1952), Ore (1960), Jung (1978), and Nash-Williams
(1971). The idea was to show that the global concept of Hamiltonicity can,
under rather general conditions, be captured by local phenomena, using the
structure of balls of small radii. (The ball of radius $r$ centered at a vertex
$u$ is a subgraph of $G$ induced by the set of vertices whose distances from
$u$ do not exceed $r$.) Such results are called localization theorems and
present a possibility to extend known classes of finite Hamiltonian graphs.
  In this paper we formulate a general approach for finding localization
theorems and use this approach to formulate local analogues of well-known
results of Bauer et al. (1989), Bondy (1980), H\"aggkvist and Nicoghossian
(1981), and Moon and Moser (1963). Finally we extend two of our results to
infinite locally finite graphs and show that they guarantee the existence of
Hamiltonian curves, introduced by K\"undgen, Li and Thomassen (2017).
