A Q&A act is one of the strongest things a mentalist can do. Its basically the performer 'mentally' reading and answering questions that are in the audiences mind. So the audience sit down after writing some questions on a card thats sealed in an envelope, and the mentalist is able to answer that question with out looking at it. The best I've ever seen live, was Luke Jermays and Derren Browns (see his 'An Evening of Wonders'). There are methods that are extremely different from each other, to go through them would take hours. If you can, watch the show I mentioned online or on his DVD and get the general idea. Corinda has a whole chapter on the matter. Jermay has his DVD set which teaches you his method in detail. Hope this helps, let us know if you want more info