Choose whether the situation needs an ongoing/habitual action or one completed as a whole.
Imperfective verbs present an action as ongoing, repeated, habitual, or simply in progress: Svako veče čitam. “I read every evening.”
Perfective verbs present it as a complete event or result: Juče sam pročitao knjigu. “Yesterday I finished reading a book.” Perfective verbs do not have an ordinary present meaning; their present-looking forms normally point to the future.