To make something slightly more complicated, let's make our own Smart Playlist by going to the iTunes File menu and selecting New Smart Playlist. iTunes shows us a new window with the playlist instructions.
Now, let's say we want a playlist that will automatically collect all of our highest rated rock songs. There's a couple ways to go about this, so don't feel like you have to be exact. There's no harm in trial and error.
For this example, let's use the first instruction to tell the Smart Playlist to look for songs with the word "rock" in the genre description.