First-time buyer: Sector 34B mein property kaise shortlist karoon?

Spent the whole Sunday checking out options in Sector 34B. First time buyer hoon, so kafi confusions hain. Dekha The Uppal Group ke kuch projects bhi, but resale aur new launch mein abhi bhi confused hoon. What things should I really check before finalizing? Kya koi hidden costs hote hain jo builders nahi batate?