When you start to type a question, Google shows related questions in a sidebar to prevent the problem of duplication. You can set the number of points you are willing to offer for the right answer and the number of days the question remains active. Each question needs to have a list of labels, so it's easy to find related questions.
To find a question to answer, you can perform a search, browse the most recent questions or subscribe to the labels that match your interests. You can't add an answer after a question is closed.
The service has a pretty smart system for rewarding good answers. Each user can rate up to 20 answers a day. For answering a question you get 2 points, but if your answer gets 5 stars, you'll earn 10, 20 or 30 points depending on the number of people that rated your answer. You also get 5, 10 or 15 points for a 4-star answer, 1-3 points for a 3-star answer. For a bad rating, you lose between 3 and 15 points.
The blog of 3form, another free knowledge exchange service, reviews Google's new Q&A site:
"It is remarkable that Google had chosen Russia to test the new service, as Russia is the country where the concept of this kind of service originated. (...) After a quick look at the new Google Q&A service I can say that technologically it closely resembles Naver and Yahoo Answers. I found the main differences in reward structure, style, and user interface. Google seems to have a cleaner user interface, that would be a reason to prefer the Google service over others everything else being equal. The effectiveness of such social search services depends on the community of participants they attract and the efficiency of the technology supporting the exchange of knowledge. Among two technologically very similar services, like those provided by Yahoo and Google, the one that will be able to build a more diverse and motivated community of participants will be able to provide a better service to them."
If successful, Google Q&A could expand globally. For the moment, Yahoo Answers is the most visited Q&A site in the US, with 96% market share in December 2006, according to Hitwise. Yahoo heavily promoted its service and managed to create a strong community.
{ via Google Blogoscoped }