Taking photos that incorporate reflections, you can achieve some amazing imagery. Perfect reflections, warped perceptions and just a different way of looking at things can create beautiful effects. Photograph your scene as it is reflected in water, mirrors, musical instruments, sides of glass buildings, Christmas ornaments or any other shiny surface (one of my favorites is morning dew or rain drops...you'll need a macro lens for this).
What issues will you run into? Not too many. Composing a photo with reflections is governed by the same guidelines as a photo without reflections. You do need to be more careful with exposure. Exposing a photo for the the reflection can lead to a somewhat washed out surrounding in bright light. On the other side, exposing for the scene runs the risk of a dark reflection.
It helps to think of this in terms of depth of field. Do you want both the reflection and the surroundings to be sharp? Or do you want the reflection to be the priority? Use the same photo techniques that you would to accomplish these effects and you should be in good shape. Above all, experiment. This results can be incredible and fun.