Nowadays computers have became an important channel of communication for handicapped people through chat, social networks, blogs, digital newspapers, magazines, and wikipedias. Switching devices combined with virtual keyboards allow the physically impaired user to operate many applications that are not adapted to disabilities. In this paper we describe the many heuristics included in the virtual keyboard Casandra. Experimental results show how useful such heuristics are. The handicapped user may reach the speed of 4.1 words per seconds using all the heuristics.