Use medium to small apertures (large f-stop numbers like f/8 to f/11 or higher) to obtain sufficient depth of field and increased image quality. Be aware that large f-stop settings create beautiful star effects on street or building lights while large apertures (small f-stop numbers like F/5.6) minimizes that effect.
Interested in reading more about skyline reflections and how to effectively incorporate them in your night photography:
Good light and happy photo making! Juergen