What are symptoms of smoking cancer. What should I know if I might have cancer from smoking?

Depends on cancer. Smoking can cause different cancers. Each type has different symptoms. Smoking is mostly linked with lung, head & neck, esophagus cancers. But carcinogens are also in the blood and not just smoked and as such your risk of even prostate and other cancers also go up. Besides heart and vascular diseases also, it's best never to smoke or quit as soon as possible.
COMPLICATED. Lung cancer is not the only cancer associated with smoking. Smoking can increase your risk of mouth, tongue, oropharinx, esophageal, stomach, pancreatic, kdney and bladder cancer to name a few. Best thing to do : stop smoking and get a physical exam.