Most people are diagnosed after going to see their GP when they notice symptoms. Your GP will examine you and arrange for you to have tests. If your GP thinks your symptoms could be caused by lung cancer, they will arrange for you to have an urgent chest x-ray or possibly a CT scan.
It may take a few days to get the results. If the x-ray shows anything abnormal, your GP will refer you to a chest specialist urgently. You should see the specialist within two weeks.
Sometimes GPs may make an urgent referral before getting the result of the chest x-ray.