It's been my experience that finding a good fitting Cadet style hat is difficult and even if you can find one that fits correctly, I've found that there is usually some other problem either with the quality of the manufacturing or something else won't be quite right (crooked bill, uneven tops, etc.) This lead me to create my own, and since it's winter time here I made it out of fleece.
Step 1: layout of the main part of the cap
first you need to lay out the fabric and mark it for cutting. Because I created a hat with a special logo on the front my cutting is a bit more complicated, but the basics are as follows:
1. Measure around your head where you want the cap's bottom to be. Write this down somewhere you can get to it later because if you ever want to make more hats you'll appreciate not having to remeasure. For my hats I normally create one strip of fabric 23" long by 5.5" tall (I wear a size Small-Medium hat normally).
2. Using a ruler and a marker or pencil mark your cutting lines on the fabric
3. Cut out the strip(s) of fabric (in my case I made 3 pieces: two 10"x5.5" and one 4"x5.5" but normally I would only make one 23"x5.5" strip)