Early and accurate diagnosis of Alzheimer’s disease, which is the most common cause of dementia, is of great importance, as it allows pharmacological treatment of patients with dementia due to this disease. Unfortunately, it is often a long-term process, mainly because of the lack of access to specialists, limited possibilities of additional tests and, above all, the lack of knowledge about the nature of this disease. Sometimes, due to an atypical clinical manifestation, the diagnosis is delayed, preventing timely introduction of pharmacological and non-pharmacological therapy. Obtaining a diagnosis in the preclinical stage of the disease enables the implementation of methods delaying the onset of dementia, mainly by increasing cognitive and physical activity, caring for the physical and mental health and adjusting the diet. These are the only modifiable risk factors for the development of dementia caused by Alzheimer’s disease, as opposed to genetic conditions, age, the number of years of formal education, and a history of brain disorders. The article presents the clinical picture of Alzheimer’s disease in its most common form, mainly presenting with episodic memory disorders, while also providing information about rare, atypical variants of this disease, such as posterior cortical atrophy, logopenic primary progressive aphasia, and the frontal and variant with corticobasal syndrome (dominant apraxic symptoms). The latest diagnostic criteria and the detailed diagnostic workup for dementia are described, and tips facilitating correct diagnosis are given. Particular attention has been paid to the role of information provided by the patient’s caregiver, decompensation factors and the practical use of popular cognitive screening methods. The paper also discusses the most common causes of diagnostic difficulties, including the influence of the natural aging process, somatic burden, and mood disorders on the cognitive state.