*Note: Unfortunately my photos of Delhi were corrupted. Feel free to Google.
Delhi is one of the largest cities in the world, so it worth preplanning your lodging in relation to what you want to see. This is doubly true if you want to avoid the metro system (traffic is a nightmare), and if you are there in winter, as the air pollution can make being outdoors unbearable. Getting around Delhi is most efficiently done via the metro, but otherwise Uber and Autos (tuktuks) are the easiest methods. Because the metro made getting around so easy, my daily itinerary may not make much geographical sense for someone travelling by car.
Day 1: Ashkhardam and Dilli Haat
Askhardam is a Hindu temple, and although it is of modern construction, the sheer size of the complex is unbelieveable. Unlike other sites in India, there are information cards for visitors, and the site is modern enough to host IMAX viewings. In contrast, Dilli Haat is permanent open air food and crafts market with rotating stalls. Although you will not be getting great bargains, the prices aren't unreasonable as the market is run by Delhi Tourism, who ensures the authenticity of the market wares.
Day 2: Rajpath and Chandni Chowk
The Rajpath is effectively the national parade grounds. Of note, the India Gate, which is effectively India's Arc de Triomphe bridges the roadway, which starts at Connaught Place, or "downtown Delhi" in the modern/western sense of dowmtown. Both are worth checking out, and Rajpath itself has gardens on either side thatmake for a pleasanat walk.
Chandni Chowk is a market in old Delhi, which is not for the faint of heart; it is frenetic, packed with people, and dirty (even for India). Keep your wits about your for pickpockets, and consider getting a guided food tour, as some of the stalls have been perfecting their foods for generations.
Day 3: Sanjay Colony and Hauz Khas
Sanjay Colony is one of many slums in Delhi,. Various tour opertaors give guided tours of the slums to break down the negative stereotypes associated with them, and to show the day-to-day life of the citizens. Of note, different tour opertaors contribute differently to initiatives in the slums, and I suggest researching whta they do with the proceeds of your tour. My tour operator of choice was RealityTravels.
Hauz Khas is effectively party central for Delhi, with numeorous clubs and pubs all over the village. While there are some historical sites in the area, it's not really what you'll be going there for - though they're worth checking out if you need to kill time before the veening begins.
Flights into and out of Delhi will arrive at Indira Ghandi International airport, which is not terribly close to anything in the city, so be prepared to take the metro, a bus, a cab, or an Uber. With regards to trains, there are two main stations: New Delhi (in New Delhi) and Delhi Junction (older Delhi). The stations are not very close together, so I would recommend making sure which is closer to where you want to go. There are also numerous local stations between them that may make a can to your destination a little shorter.