This is a beginner hat pattern, its crazy easy and you only need to know how to knit and purl.

This will usually fit people from ages 7 and up. If you want it for kids younger than 7, just take away 10 stitches. Also the pattern for the giraffe hat is below as well.

This is a straight needle hat pattern

I use usually what i have left of yarn from sweaters i made and stuff like that, you can use any yarn you want in any size you want although i would suggest medium 4 or bulky 5.