1. Do your research.
You don't need to know the differences between Captain Marvel and Captain Marvel and Captain Marvel (you get the idea) but you should at least know your own interests. Do you want teenage angst or do you want teenage angst with magic, mutants, and monsters? Do you want something familiar or do you want to jump into something you've never heard of? Is good writing or good art more important to you, or do you require both? If you know the basics of what makes you a happy reader, your trip to the shop will be a lot easier.
2. Go with a friend.
Granted, your friends may be jerky snobs but they can tough out a few minutes in the corner of a store while you embrace a new hobby and make your life a fuller, better... I said five minutes! No, we just got here. God, stop embarrassing me!
Channel the Amazons. Wonder Woman would never lose her cool.
3. Ask for help.
I know subcultures can be intimidating when you start sniffing around the front gate, but geeks love to (over) share! They all have their favorite series, characters, artists, etc. and they want you to love them just as much as you do. And if you think they're being mean or you are absolutely terrified, pop a Xanax (prescribed only, of course) and go somewhere else. Hell, Barnes and Nobles sells graphic novels and a small selection of single issues. Also, you can always start your collection with the Comixology app or online shopping. Which brings us to Rule #4.
4. Whenever possible, shop local.
If you can do it for food, you can do it for comics. They are equally important. Comics will usually be cheaper and easier to find online, but if you want your local geeky community to thrive, you gotta invest. Plus, your local shop will come to learn your taste and will help you cultivate a killer pull list or automatically put things aside for you because they think you'll like it.
5. Don't carry your giant stylish purse into a shop.
Some shops will make you check them at the counter and others will kick you out while everyone stares because you happened to spin around too fast and your bag took out an ENTIRE WALL of comics, books, and toys. Not that that's ever happened to me or anything...
Longbox of shame.
If you're still a nervous wreck after all of this fabulously helpful advice, fake it 'til you make it. Big heels, big sunglasses and a supermodel strut will take you far. It's pretty much how I deal with all emotions. Good luck!