Now that you know how many mezuzahs you need, do some research to find the right place to purchase your mezuzahs. Because mezuzahs must be made according to very exact laws and specifications, only an expert can determine if a mezuzah is kosher.
Some basics: The mezuzah must be hand-written by a competent scribe on specially prepared parchment with the specific types of quill and ink mandated by tradition. All too often, printed or improperly prepared mezuzahs--or even empty mezuzah cases--are fraudulently sold. So make sure to purchase your mezuzahs from a trusted religious source, or ask your rabbi for help.
The mezuzah scroll is then rolled from left to right and placed right-side-up in a protective case.