Delhi is large enough that where you look matters. Here's what's currently listed in the areas that come up most often — click through to any of them to see the live listings.
Saket (29 listings) has the most listings in South Delhi right now — worth starting here if you're in that part of the city and want the widest choice.
Karol Bagh (25 listings) has the second-highest count in the city and is well-connected by metro if you're coming from elsewhere in Delhi.
Aerocity (22 listings) is the area to check if your flight timing means staying close to the airport — plenty of profiles based there can either come to your hotel room or host you at their own place nearby, whichever suits your schedule better.
Dwarka (18 listings) is worth checking if you're actually staying in southwest Delhi near the airport rather than central Delhi.
Hauz Khas (13 listings) makes sense if you're already out for the evening around Hauz Khas Village and want someone close by rather than arranging transport across town.
Connaught Place (11 listings) is central and easy to reach if you're already downtown for the evening.
Paharganj (10 listings) sits right next to New Delhi Railway Station — convenient if you're staying in that budget-hotel corridor.
Vasant Kunj (8 listings) has fewer listings currently, but is worth checking if that's specifically where you are in South Delhi.