...are standardized tests available for purchase. Often, these tests must be purchased in quantity and the producer may not want the test available to the general public, or for copying.
Examples: SAT and the Beck Depression Inventory.
... are generally not for sale and appear in a journal, thesis, dissertation or book.
Examples: MAST (Michigan Alcoholism Screening Test), Schaefer Parent Behavior Inventory, and the Family Adaptability and Cohesiveness Evaluation Scale (FACES-III).
The American Psychological Association also has an excellent site with frequently asked questions about finding tests.
To administer a test that you have found: