My ancestor lived in XXXXX Borough/Census Area. What should I do to find more about him?


The fact that you know the borough or census area is actually a major step.  You'll find a listing of all the boroughs and census areas on the boroughs page or can access all of them via the clickable map.  You'll want to visit the area of interest  to see what information is there.  If someone has adopted the borough/census area, s/he will probably have added material that just might be of help to your research.