How to Wear Hats
Find your style. Hats are not an everyday item like they used to be so people are uncertain about how they should fit. Don't let the uncertainly overwhelm you. High crowns, low profile, short brim, wide brim, floppy, structured, modest, flamboyant -- there are too many styles out there for you to honestly look bad in all of them. So find the shape that works for you, and do listen to your girlfriends who tell you the hat looks fine.
Mind your hair. People talk at length about making sure your hat flatters your face shape*, but you can't forget your hair. It's even more of a frame when wearing a hat. Wearing it long and straight may be your best option, or maybe you should curl and pin it close to the brim. It all depends on the hat you buy. Likewise, you may not be able to wear a few styles with your trendy cropped hair lest you look like you're a cancer patient.
Beware of what else is going on around your face. If you are planning to wear a hat all day, don't also wear large earrings, a big necklace, and a dramatic collar. Your head is not an accessories store.
Ignore critics. Hats aren't as popular as they used to be, and some people will think you are very strange for wearing one. I wear a beret instead of a knit cap as my winter hat, and I can't even begin to count the number of people who have either made Pepe Le Pew jokes or asked if I speak French. Seriously. That's happened. These people are stupid and ignorable. If you like something, wear it with confidence and ignore the maddening crowd.
*Not really a fan of the article (your face isn't flawed), but that's what those articles will usually say.