To find out if you have asthma, the doctor/nurse will ask you to describe your symptoms and what makes them worse or better.
They will ask about any childhood breathing problems, any allergies you have including hayfever and eczema, any breathing problems in the family, any pets and the jobs you have done over the years. They will also ask about smoking, any medicines that you take on prescription or buy at the chemist, and about other longer term conditions you have.
The doctor/nurse will do a physical examination and listen to your breathing using a stethoscope. They will then ask you to do some breathing tests.