The interaction of a liquid with a surface is of fundamental importance to many areas of scientific research. Information on the properties of liquids at surfaces at the microscopic scale is also required to elucidate the mechanisms behind macroscopic observations. In this study, the atomic force microscope (AFM) was employed in various complementary modes of operation to investigate the properties of nanometer-scale oil droplets existing on a polystyrene surface. Force curve mapping was used to gently probe the surface of the fluid droplets, and through automated analysis of the force curves the true topography and microscopic contact angle of the droplets were extracted. The contact angle was found to be 13 +/- 2degrees, which is in excellent agreement with values obtained from macroscopic measurements. A discrepancy between these values and contact angle values obtained from tapping mode images were attributed to deformation of the soft interface. The resultant phase contrast mechanisms in the liquid tapping mode images are discussed and are attributed to energy dissipated in the deformable oil-water interface. The interfacial tension of this oil-water junction was then measured using the AFM and again found to be in close agreement with theory and macroscopic measurement. Finally, using the above information, the force exerted on the sample by a scanning tapping tip in fluid was derived and compared with forces experienced during tapping mode imaging in air. The presented data thus demonstrate the complementary nature of the employed imaging modes for the investigation of liquid interfaces and illustrate the benefits of a combined surface analytical approach for their characterization. We also highlight the ability of AFM to both measure interfacial properties and investigate the topography of the underlying substrate at the nanometer scale, indicating its potential to improve the understanding of the effect of surface topography on such properties.