What are the symptoms of cancer? Blood in stool?

Too broad a question. Cancer at each site has specific symptoms. Frank blood in stool is usually not a common symptom of even colon cancer. Some common symptoms are weight loos, weakness, mass or lump in an organ, change in bowel habits, cough etc. You may wish to be more specific in your question as to what type of cancer are you concerned about.
Need to know more. Different cancers have different symptoms; blood in stool may be one, but it is also very common in the absence of cancer.Please ask your question with more specifics, and the answer will be more helpful.