Most homeowners are not, and that is fine. Book a sweep and inspection. It establishes the condition of the chimney and tells you whether anything else on this page applies to you. If you already know what is wrong, go straight to the relevant service.
Chimney Cap Installation
Stainless or copper caps sized to your flue, keeping rain, animals, and debris out of the chimney.
Could be a blockage, a creosote-restricted flue, a damper problem, a poorly formed smoke chamber, or insufficient chimney height. Start with an inspection. The causes look identical from the living room and are cheap to distinguish with a camera.
Water stains near the chimney
Usually a cracked crown, eroded mortar, or lifted flashing. See chimney repair. Sealing before finding the entry point makes it worse.