Delhi's restaurant scene is improving at very fast pace. Numerous restaurants open up every month. These days even fantastic Italian or Thai restaurants have started, much to the relief of the big diplomatic crowd. Besides, Delhi's vendor stalls offer all sorts of food, ranging from deep-fried poppadums to fresh fruits. Of course, there is always a local restaurant where one can try the curries or thalis. Also, it won't cost you an arm and a leg to eat at these "local" restaurants. Furthermore, be aware that generally, food is cooked and served with a profusion of spices, something that might be par for the course for the locals but might be bothersome (that's putting it mildly) to an outsider. There are also many Bars in Delhi.
The same goes for meat at the vendor stalls: some people can fall sick by simply looking at it, while others can eat to their heart's content. It is quite common for both locals and travellers, to eat at hotels. Unlike in the West, hotels in India/Delhi often feature above-average food; one reason for this might be the need to maintain a reputation among the steady stream of foreign and richer Indians staying there.
There are many famous Restaurants in South Delhi. In Delhi particularly in the South Delhi ask any body who is not aware about Rajinder da Dhaba near Kamal Cinema, Safdarjung Enclave, New Delhi. So are the traditional resturant chains like Haldiram's, Nathu's, Bikaneriwala, Evergreen at Green Park, Bengal Sweets at South Ex-I, Mc Donalds, Nirulas, Domino's, Sagar Ratna, Karim's etc.
Particularly in Delhi one can be assured for the quality of foods, they are much better in quality than any part of the country. One must try the chole kulche from some famous out lets. One must not say no to Papri Chat, Tikkis, Raj Kachori, Kulfi Faluda etc. they are really mouth watering.