I learned how to make hats with a loom about a year ago, and now I've made over a dozen for friends and family. This one is for a 16 month old girl. I bought the Loom Kit at Wal-Mart in the craft section by the yarn. The kit is about $17 and yarn cost $1-3, so after you buy the kit it takes less than $5 to make a hat! Warning: it takes me an average of 3-4 hours per hat so I do it on long car rides or while I'm watching tv.
For the rim... I use 17 rows.
For the rest of the hat... I use 20-24 rows.
For the pom pon... I wrap the yarn around four fingers.
This is what the loom looks like. The green is for adults and red is for toddlers.
Tips: I like to use thicker yarn (like I used on the toddler's hat). It's also fun to double up two colors at the same time to create a "peppered" look. Mix colors, play with different size rows, and be patient.
Sorry that I'm not very detail with instructions on how to make them. When you buy the Loom Kit it comes with better instructions!
Here's a link to the Loom Kit sold at Wal-Mart: