The forms that most schools require along with the letter. This form usually includes a waiver of your right to view the letter, which you should sign. Be sure to fill in all the students parts of the form. These forms or often available online in PDF or other format. Faculty are busy doing many different things and are often working against deadlines, so they sometimes forget.
Email is also very effective.
Letter writers differ in how long they keep your letter in paper or digital form. Florida Tech does not have a centralized recommendation letter repository. If you expect to use the letter again, ask the write to hold on to it. Few faculty reveal their letters to students as a matter of policy.