Organometallic halide perovskite solar cells have emerged as a versatile photovoltaic technology with soaring efficiencies. Planar configuration in particular, has been a structure of choice thanks to its lower temperature processing, compatibility with tandem solar cells and potential in commercialization. Despite all the breakthroughs in the field, the optical mechanisms leading to highly efficient perovskite solar cells lack profound insight. In this paper, a comprehensive guideline is introduced involving semi-analytical equations for thickness optimization of the front and rear transport layers, perovskite, and transparent conductive oxides to improve the antireflection and light trapping properties, and therefore to maximize the photocurrent of perovskite solar cells. It is shown that a photocurrent enhancement above 2 mA/cm2 can be achieved by altering - reducing or increasing - the thicknesses of the layers constituting a CH3NH3PbI3 (MAPI) type perovskite solar cell. The proposed guideline is tested against experiments as well as previously published experimental and simulation results for MAPI. Additionally, the provided guideline for various types of perovskites can be extended to other direct band gap absorber-based solar cells in superstrate configuration.