Optional Reading:

Interestingly enough, I often see the sign "DID." This sign is obviously an English intrusion, but the fact is that many ASL signers use this bit of lexicalized fingerspelling from time to time. Notice how the pinkie comes up but the index finger doesn't come down (for the letter "i").  I don't recommend you use this in your ASL classes, but if you plan on hanging out with any Deaf people, it is a nifty little sign of which to be aware.

Animation: "did"