While in Delhi, i went to a travel agents and booked a car and driver for my few days there so i could get a quick look around most of the major sites. I have to say, he was a nice chap who drove me around, he knew all about the places i wanted to go, and he did make my few days there enjoyable..... the only complaint i have, is the tour guide/souvenir shop relationship. Obviously he had a commision from a certain shop from whatever i bought there which i do not really mind, it is just that he constantly wanted to take me there. I went once, and did buy a few things... but in all honesty, after looking around other places, the things i bought were all vastly over priced... i got much better deals off people selling things on the streets. You can haggle the prices a bit, but it is still expensive even though you think you have got it cheaper. The staff in the shop were all really pushy too, wanted me to look at everything and buy it. My tour guide in Agra for the day was really pushy aswell as the shopkeeper... came close to losing my temper there. So, if your looking to buy any souvenirs... make sure you shop around first.
If you use the so called prepaid tour guides at the Red Fort... beware, you pay twice - Once for the actual tour guide, and then once they have taken you around... they give you the speach about 'good people give things to other people'... and well 'I've done my job well, and you're a good person - so you should give me a good tip'
If you take a tour, your guide is probably going to bring you to a tourist shop where they will aggressively try to sell you expensive items like carpets. Your guide of course gets a commission. They do not take no for an answer so be prepared for an annoying session. And by the way they always bring you to these shops as a learning experience like 'watch how we make carpets.'