How can I guarantee a hat drop?

How can I get a hat? I've been playing for ages, and haven't got a darn tootin' thing.

While a real drop cannot be guaranteed, you can craft yourself a hat.

3 refined metals will craft into a random hat. 4 refined metals and a class token will craft a class-specific hat.

It takes two drops to create a scrap metal, three scrap metal to create a reclaimed metal, and three metal to make a refined metal. A class token is created by crafting three weapons of that class.

So for a random hat, it takes at minimum 54 items. For a class-specific hat it takes at minimum 75.

For more crafting detail, visit the official wiki.