The multitouch technology is emerging as a trend in recent years. The multitouch interfaces allow interacting with a virtual object directly, similar to a real object. However, this technology has not only advantages. There are several issues to be resolved, such as the accuracy of the manipulation, the occlusion, the separability of the manipulation, etc. The multitouch interfaces allow multiple spatial transformations that can be performed on a virtual object with only a gesture. For example, an object can be rotated, translated and scaled with two fingers with a single gesture. However, some unwanted movements may occur accidentally. The technique of separability appears with the intent to prevent unwanted movements on multitouch surfaces. Occlusion is another problem that occurs in multitouch interfaces. Often the user s hand hides the vision of the object with which he/she interacts; or the user s action on interface hinders the movement when it clicks on a bottom that triggers action. This dissertation studies, proposes and evaluates two techniques of separability, aiming to reduce the problems that arise due to excessive freedom of manipulation in multi-touch interfaces, and evaluates the efficiency of these techniques. The techniques developed are not only applicable in simple virtual objects; they are also for WIMP (windows, icons, menus, pointer) objects, aiming to reduce occlusion. A series of tests was performed to evaluate precision, occlusion time for completion of task, and ease of use.