Due to its nonperturbative character, the theoretical modelization of strong field phenomena is a challenging aspiration. In this chapter, we shall consider the problem of high-order harmonic generation and propagation, and review some recent proposals that conform an alternative approach to the standard procedures. In particular, the semiclassical description of the single-atom response can be nowadays replaced to include the full quantum description. Also, the limits of the Strong-Field Approximation can be extended to include the influence of the strong field on the ground state. These two aspects allow for a new procedure, here referred to as SFA + , for calculating the high-order harmonic generation spectrum, which is demonstrated to improve the quantitative accuracy and to recover, for instance, the correct dependence of the harmonic yield with the laser wavelength. On the contrary, the problem of harmonic propagation has also been tackled recently from a new perspective: the combination of SFA + methods with a Discrete Dipole approach. This latter strategy is not based on the differential wave equation for the fields, but on its integral version, and finds some advantages with respect to the usual approximations (slowly varying envelopes, paraxial, etc).