Things that are repeated to us over and over again tend to stick with us. For instance, have family members see if they can complete several ad slogans, like these:

Melts in your mouth, not in your hands............................M&M's
Two all beef patties, special sauce, lettuce........................McDonalds Big Mac
Yo Quiero...............................................................................Taco Bell
Mmm, mmm, good...............................................................Campbell's Soup
Just do it................................................................................Nike
With a name like _____....it has to be good.....................Smuckers
Be all that you can be...........................................................U.S. Army
Breakfast of champions.......................................................Wheaties
It keeps going, and going, and going...................................Energizer

Teach that you must be careful about what goes in to your mind. You should always be prepared to have something good to put in to your mind in case something bad pops in. Music is a good way to do this. 

Here is a talk by Boyd K. Packer (April 2008) that mentions how the mind is like a stage and how to get rid of bad thoughts. He also suggests music as a means to help. Great article to draw from for this lesson. 

Demonstrate the idea of the mind being like a stage by using a small, simply constructed stage and finger puppets. Visually show the family Boyd K. Packer's words by acting it out as you share the idea. Have some puppets designated as bad thoughts, others as pure thoughts. Show how the pure thoughts can oust the bad ones.

Spend time memorizing Church hymns and children's songs here. Memorize scriptures using songs here. (all scripture songs are free)