The paper provides the developed approach to solve the eigenvalues and eigenfunctions problems for the Helmholtz equation in domains with an arbitrary configuration. In developing the approach for numerical solution of problems, the point-sources method (PSM) was used. The proposed method is based on the analysis of the condition number of the PSM system or the error of the numerical solution of problems. The concept of "eigenvalues criteria" is introduced. The research result is a developed effective method -an algorithm for solving problems of eigenvalues and eigenfunctions for the Helmholtz equation. It is shown that at the approach of the Helmholtz parameter to the problem eigenvalue, the condition number of the PSM system and the error of the numerical solution rise sharply. Therefore, we calculate the dependence of the condition number of the PSM system or error of the problem numerical solution on the Helmholtz parameter. Then, according to position of the maximum of the received dependences we find the eigenvalues of the Helmholtz equation in a given domain.. After finding the eigenvalues, it is possible to proceed to the determination of the eigenfunctions. At that, if the eigenvalue appears degenerate, that is some eigenfunctions correspond to it, then it is possible to find all the eigenfunctions taking into account the symmetry of the solution domain. The two-dimensional and three-dimensional test problems are solved. Upon the results obtained, the conclusion about the efficiency of the proposed method is made.