Read the brief intro about the series in previous post.
Eating style and practices
The another not properly understood topic about Indian culture is the Eating habits. Many people in met during my Brazil trip had an understanding that Indians don't eat Beef (cow meat) because of sacred reasons but other meat is fine. For a country like Brazil or Argentina (as I was told) vegetarianism is a very rare concept. To some extent people would claim that you can't survive there without meat or that you will only be eating fruits and raw veggies. As you can read on my post on Brazil this was not so.
So the question about Indian not eating beef: Well, again there is nothing like an Indian religion, we have people of multiple faiths and religion in India and all of them have different sacredness rules about food. The Hindus (the majority as can be unambiguously mentioned at time of writing) don't eat beef. Before I go to other religions its a point to be mentioned that Hindus themselves have many more sub-groups which have varying levels of restrictions beyond beef. For e.g the Brahmans and Vaishnavs don't eat meat at all.
The Muslims similarly don't eat Pork/Pig meat (In fact the rules are more strict to include only halal meat), I don't know of any eating restrictions in Sikhism and Christianity, which are the next 2 major religions in India. My family follows Jainism which is another religion. Jains are considered part of Hindus in a broader categorization which counts only 4 major religion, but we have much different guidelines as far as food is concerned. Jains follow restricted vegetarianism mean they don't eat some veggies for e.g root vegetables. I realized reading wikipedia that some Jains have follow Veganism.
As you would expect most of these are religious guide lines and people follow them to varying levels. But one thing to understand is that while Vegetarianism is pretty common in India veganism is not so common. So for most people milk, milk products and cheese are very regular part of the meals.
Eating by Hand.
A friend of my host in Brazil was probably shocked and puzzled to see that I was eating Tapioca with Knife and Fork and the underlying debate which was in Portuguese lead me to think I was expected to be eating with hand instead.
This particular debate was difficult to handle as I didn't really understand the reason of eating with hand except that some Indian food really is most easily eaten with hand like Rotis(Chappatis), Naan(bread) and Dosa much like Sandwiches and Burgers. For other food like Rice the eating practice is very regional and matter of choice again. My father insisted us to learn to use spoon to eat rice pretty early in childhood (you don't usually need fork and knife for vegetarian food) and thats very typical way of eating in formal dinning or parties.
That said many people do eat rice and curry with hand and its very common in authentic southern Indian eating style to do so. Of course people adapt themselves according to places and situations, and therefore the eating style becomes western when you are in the west.
Coming to the reasoning part of it, I have found couple reasons as I searched on the net, one is what I commonly heard earlier that you can enjoy the food most when you eat with hand, 
It should however be noted that strange as it may sound people in India were pretty well aware of "Washing the hands" and similar hygiene even before people in the west started bothering about them due to Swine flu. Its very much part of the food habits to use soap or such to wash hands before eating food specially when you are not going to use cutlery.