Depending on the entity this occurs through a method of words spoken and/or written, certain actions or movements being performed, and most importantly the education & training in conjuration that allows you to perform a conjuration effectively.
As there are thousands of entities to consider not all methodologies can be reviewed, however, there are often multiple ways to conjure one type of spirit or one race of spirit. You can conjure a specific entity within a race or you can conjure an entire race. For example, you can conjure the goddess Aphrodite, you can conjure the primordial, Grecian gods, or you can conjure the entire Grecian god hierarchy. Another example, you can conjure a Marid Djinn, or all Arabian Djinn, or all ancient, Arabian Djinn, etc. Depending on the conjuration & actions involved depends on the broad or specific terms through which you are working with a spirit or race of spirits.