The potentials of mean force (PMFs) for the solute pairs in ambient water were reported by lots of computer simulation studies, where different simulation methods and various models were used. It turned out that the resultant PMFs are quite sensitive to both the methods and the models employed. In the present study, we selected with great care a set of molecular dynamics methods and models and then carried out the computer simulations to obtain the more reliable PMFs for methane-methane, Na+-Cl-, Na+-Na+, and Cl--Cl- pairs in water. We will thoroughly compare our results with those of other researchers to validate our set of simulation methods and models for PMF calculation.