I love my black car, it looks awesome when it's clean.  But black cars show everything..  Here are my top tips for a black car:

1.  Use proper wash and dry technique to reduce scratching.  I use 2 buckets with mitt slides in each, one bucket fill with water to rinse my mitt, the second with soap.  I use the reef wash mitt, and dry with the performer drying towel (my fav).  

2.  Layer protection.  I layer chemical guys blacklight and Autostolz Enhanced wax on mine, for more shine double up on the layers.  Other good layers are Jetseal, butter Wet Wax, and Black wax.  Like Sarah lea, layer upon layer upon layer.  Layer on the awesomeness.  It will make it easier to clean and add more and more shine and depth.

 This is a picture of my black van (the silver car is the reflection).