Despite the recent discover of genome-editing methods, today we can say these approaches have firmly entered our life. Two approaches-knocking out malfunctioning gene allele or correcting the mutation with precise knock-in-can be used in hereditary monogenic diseases treatment. The latter approach is relatively ineffective. Modern data about the ways of repair of double-strand DNA breaks formed by nucleases are presented in this review. The main part of the review is devoted to the ways of increasing precise and effective knock-in: inhibition of non-homologous end joining and stimulation of homology-directed repair key factors, use of small molecules with unknown mechanism of action, cell-cycle synchronization and cell-cycle-dependent activity of Cas9, donor molecule design, selection, alternative methods for insertion and other approaches.