American Sign Language

Family
MOM:
Make the sign for "Mother" by placing the thumb of your hand against your chin. 

Your hand should be open (a "5" shape).

Note: there are several variations of the sign "MOM."  

An interesting method I've seen is to place the tip of the thumb of your right "A" hand on your chin then open the "A" hand into a "five" hand.

Some people wiggle the fingers while signing MOM.

Some people use a double tap on the chin.

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.

DAD:

Make the sign for "father" by placing the thumb of your hand against your forehead. 

Your hand should be open.

For the sign DAD you can use a slight "tapping" motion to touch the thumb to the forehead, move the hand out an inch, then touch the thumb to the forehead again.  You don't have to "tap" it.  You can just touch your thumb to the forehead for a moment. You don't even need to make contact with the forehead as long as you get it relatively close.  Some people "wiggle" the fingers--it means the same either way, wiggle or no wiggle.

Note: Some people say that the "wiggle" makes the sign more intimate as in "papa" but that isn't widely established.

Some people start with an "A" hand and open into the "5" hand.  I just stick a "5" hand up there.

To do the sign for "boy," grab an imaginary baseball cap on your forehead.  This sign also can mean MALE  and is one of the versions of MAN.

The sign for "Girl" is made by forming your hand into an "A"-hand and then trace along your jawbone with the tip of your thumb - starting near your ear and moving to near your chin.  If you specifically want to indicate the concept of "girl" as in "a little girl" then you can use a bent hand to show the the height of the girl.