Practice the American Sign Language alphabet from a library book or an ASL website. Visualize and say each letter out loud as you try it with your hands. Some of the letters, like "C," look like the three-dimensional letter. With some practice, you should be able to familiarize yourself with the ASL alphabet in one day.
Cut out flash cards of the ASL alphabet. Many workbooks and websites offer free flash card printouts of ASL. Test yourself with the flash cards. You will be able to recall more and more of the alphabet as you use the flash cards.
Learn a few common key phrases in ASL, such as "Good morning," and "It's nice to meet you." Common phrases are what you would use most often in a real world situation. Becoming familiar with these phrases is a way to learn sign language quickly in one day.
Watch a video song in ASL on the Internet or a public library DVD. Many popular children's songs and some pop songs are available signed. Typically foreign language classes use songs to help students learn the language faster and easier, and you will be able to learn the song within a day if you choose something you like.
Greet a friend or relative in sign language at the end of the day. Teach him some of the signs. Teaching someone else sign language will help reinforce your own ASL skills. Perform your song, too.