Variable. In early stage patients may be without any significant symptoms- -perhaps some coughs- and sometimes is found accidentally . At a later stage symptoms would be more significant -that will include- persistent cough, shortness of breath, chest pain associated with breathing ( deep breathing for instance), coughing up blood, weight loss, decrease apetite etc.
Depends. Early stage lung cancer can be asymptomatic or no symptoms. Often it is found incidentally by chest xray or chest ct scan. Ct scan screening for high risk patients has shown to be effective. Larger cancers can cause symptoms such as bleeding (hemoptysis), wheezing, weight loss and other symptoms.