Q:

What are the general patterns of child-directed speech in Japanese? 

In English, parents usually talk to their kids differently from how they usually talk.  The words they use when doing so usually ends in -y.  For example, "kitten" becomes "kitty", "I" usually turns into "Mommy" or "Daddy" depending on who the parent is, and "wakie wakie!"  is used when waking the kids up. 
Are there any patterns in Japanese child-directed speech?  How are the words changed when parents talk to their kids? 
Note: I read from other posts that s- sounds are changed to sh-, ch- or sometimes p- sounds in a little child's speech.  But do parents speak to their kids this way as well? 

A:

This question is quite broad, but of course child-directed speech also exists in Japanese. 
You probably know ～さん → ～ちゃん is said to be both children's speech as well as child-directed speech, but it is very very common in conversations with no involvement of children.  Doubling à la "wakie wakie" is also common (especially for one mora words). 
Without further ado, here are some common words/expressions used in child-directed speech:

手 → お手々【おてて】
目 → お目々  
寝る → おねんね、ねね
おっぱい → ぱいぱい
おばあちゃん → ばあば
おじいちゃん → じいじ
犬 → わんこ（ちゃん）、わんわん、わんちゃん
猫 → にゃんこ、にゃあにゃあ
車 → ぶうぶう
足・歩くこと → あんよ
捨てる → ぽいする
絵を描く → お絵描き（する）
座る → お座り（する）

