Noida property buyers: Share your negotiation hacks!

Been looking for a 3BHK in Sector 117 for myself since January. I work in real estate, but buying for myself is different. Builders ka super area vs carpet area game aur PLC charges ka drama abhi bhi chalta hai. Actual 'all-in' price kitna upar jaata hai from advertised rate? Ready-to-move projects mein bhi hidden costs hote hain kya? Resale mein negotiate karna easy hai ya new launch mein? I found some builders are flexible on PLC if you push hard, especially on higher floors. Any other such tricks or red flags to watch out for?