Keep it clean and simple, and pay attention to composition and design. Composition is nearly everything in 2D art – far more important than subject matter. Pay attention to what the frame edges are doing and how the subjects within the frame interact with them, and to the basic design being made my the positive and negative spaces in the composition. Be careful that you don't make the background clash with the human subjects. This can be done by awkward composition, a big difference in brightness between the two, too much depth of field, clashing colors, etc. In other words, open your eyes and pay attention to what is in the viewfinder. Use D of F preview if your camera has it. The rest will just be working with the subjects. This is stuff that is a given for any photo, but I am saying it in regards to this situation because it is really easy to make these types of photos really crummy with confusing/awkward compositions, because you can be concentrated so much on working with the subject.