To obtain an EU Blue Card, three main requirements must be met. First, you need a recognized degree from a German or foreign university. In certain IT professions (and other highly specialized jobs), several years of professional experience can replace the degree. Second, there must be a specific job offer, e.g. in the form of an employment contract. The contract must be for at least 6 months and provide for employment that matches your qualifications. Third, the employment contract must provide for a certain minimum annual salary.
In addition, general residence law requirements apply, including a valid passport and health insurance coverage.