Homestays represent genuine hospitality. They are the only kind of hospitality that is truly generous because it is selfless, which is a fundamental value of nomadic cultures. The principle is simple: register on one of the free lodging networks that have been popping up all over the Internet over the past several years. Then, create a network of friends and open your home to those who are passing through. It is then up to you to decide how accommodating you would like to be: pick them up/drop them off at the train station or airport, act as a guide, introduce them to your friends, etc. In short, welcome them as you would expect to be welcomed. Naturally you will also be welcome around the world in other members homes. There are no obligations, although you have the freedom to refuse any contacts or requests for accommodation.
This system is obviously dependant on trust between members and no money is to be exchanged. 100% free, 100% trust!
Moreover, without any preparation or specific intentions, homestays are the best way to discover a countrys customs and its inhabitants. This usually happens with each new meeting, unexpectedly, spontaneously. Do be cautious, though. Dont go into just any house with just anybody. Instincts are your best guide. If it doesnt feel right, dont do it.