MOM: The American Sign Language (ASL) sign for "mom"

Also see: DAD

There are a variety of ways to express the concept of "mother."  A good general version of the sign for "mom" or "mother" is made by touching the tip of the thumb of your dominant "open"-hand (also called a "5"-hand) to your chin.  You may see it tapped twice; you may see the fingers wiggle; but the most basic form is to just touch the thumb of a five hand to the chin.
 

MOM [version 1]
     

Sample sentence:  "What is your mom's name" = YOUR MOM NAME WHAT?

MOTHER (side view):

Memory aid: It might help to think of the "chief" man or woman of a family. As if the fingers of the hand were representing outspread feathers.

MOTHER (version 2):

MOTHER (version 2 side view):

MOTHER (version 3):

MOTHER (version 3 side view):

Notes: 
Also see: DAD

Also see: GRANDMA

As noted above there are several variations of the sign "MOM."  
Some people wiggle the fingers while signing MOM.
Some people use a double tap on the chin.
Some people place the tip of the thumb of your right "A" hand on your chin then open the "A" hand into a "five" hand.

You may be told that certain forms of the sign are more "intimate" than others. For example it has been claimed that the wiggled-fingers-version indicates a closer relationship.  While that may be true in some cases -- or even often enough to be considered a "tendency" -- I would hesitate to lump all instances of the wiggled-fingers-version of the sign MOM into a separate category. There is enough overlap that you should assume the signer simply means "mom" -- and rely on other clues to decide if the signer had a close relationship (or not) to their mother.