In every city I went to last year(Bangalore, Chennai, Tiruchirappalli and Mysore) I had multiple offers from people to take me around and show me the sites, usually from the drivers of the auto-rickshaws. In every museum and temple there were official (and sometimed unofficial) guides willing to take you around for a few dollars.

I usually took up the offers at the museums (In one museum in Chennai, my tour guide was a PhD student in Indian History) and only occaisionally took up some of the drivers and only if I felt confident that I had convinced them that I wasn't interested in going to any stores and wasn't planning on buying anything that day.

My best tour guide was a 10 year old boy who came up to me in Mysore wanting me to listen to him speak English. I did allow him to take me to his uncle's aromatherapy shop since he gave me a good tour of the local food market, including an interesting sidetrip to the meat market in back (no mutton for me that night!). I ended up giving him a few dollars for the couple hours he spent showing me around.