Fashion is always about what's new, but all week long BAZAAR.com is considering the old—all things vintage to be exact. Follow along for your chic guide to treasure hunting for vintage clothes, vintage bags, vintage wares, vintage wines and beyond, from the contributors who know it best. Today, Tina Craig of Bag Snob, on finding the real deal when it comes to It bags.

A good bag should last forever. Some bags are serious investments, and others are fleeting dalliances. To me, bags are like my relationships: Marry the best and have short-term love affairs with the fun ones. I also believe in enjoying your bags daily, so I don't save them for special occasions. I say wear them now! The more loved and used they are, the more character your bags will have. The way the wrinkles on a woman's face reveals her personal biography, every mark and line on my bags tell their stories.

In fact, many European women are even embarrassed by shiny new bags. My friend's mother, a chic French woman, literally goes out in the grass and jumps and stomps on her new Birkins to make them look worn and used. I don't recommend going to such extremes, but rather, borrow from your grandmother's closet. If you desire a bag with character the way I do, a vintage bag naturally worn with age will do just fine. But with so many fakes out there, one must be prudent and careful about how she shops.

It's paramount to start with a reputable source. I buy all of my vintage pieces from a select few trusted places. I love What Goes Around Comes Around NYC. With locations in SoHo, the Hamptons and Hollywood, along with a strong online presence, it's an amazing source for the rarest of bags. Owner Seth Weisser is incredibly knowledgeable on all things vintage and has a collection worthy of the Hermes museum—including this 1930s hand-painted Hermes bag. Below, he shares the best way to shop vintage:

WGACA's Authenticity Tips

1) Find a reputable seller. There are a lot of places offering luxury bags, both in-store and online. Some of these are more trustworthy than others. Our #1 tip: Only purchase from a source you know you can trust, who takes authenticity as seriously as you.

2) Trust your gut. A lot of fakes are super fakes, meaning they've deconstructed an actual bag and copied it stitch for stitch. With counterfeit items like these, the only way to distinguish them from the real deal is to take them in your hands and feel for markers of quality. Does the leather feel cheap? Is the bag oddly light? If so, don't buy!

3) Check the serial. Most luxury brands have serial numbers or other internal markers of authenticity. Chanel bags will have a hologram sticker and if it has its original authenticity card, this number will match what's inside the bag. Hermès stamps their brand name along with a date stamp somewhere on the bag. Louis Vuitton is similar; they put a date code inside of the bag stamped on a tab or the inside lining. Pay close attention to the font. If it's different from how the brand name is normally displayed, beware.

4) Compare to the real thing. The best authenticators spend years looking at thousands of bags, both from the store and secondhand, before they can claim to really know the difference. But by looking at photos of the original items, you can get a sense of how the piece is supposed to look. Look at how the bag sits, how it holds its shape, and the texture of the material.

5) It's the little things. Although a fake might look great from afar, close up is where things are a bit messy. Check the small details. The stitching should be straight, the engraving on the hardware should be smooth, and the hardware itself should not look cheap or plastic-y. The zippers can often be a dead giveaway. All designer brands have zipper brands of choice that they use in all brands, and some make their own zippers and stamp them as such. This is a small detail, but it's one fakes often get wrong.

Another store I shop at often is Fashionphile. Proprietor Sarah Davis finds the most notably sought-after bags from vintage to current seasons, and her well-priced boutique also reminds you that designer vintage need not cost you a fortune.

It's tough to find collectibles, so when you do and it's a smart price, jump on it. Keep it in near-pristine condition, and then you can sell it for a nice profit 10 years later. Keep in mind there is a major difference between a vintage bag and a used bag. It was once the rule that for a bag to be considered officially vintage, it had to be at least 20 years old. Now a bag 10 years or older can be termed vintage. Meanwhile, your Chanel bag from Fall 2012 is just a used bag. It won't reach its vintage status until 2022. Then again, it could be well worth the wait.

Fashionphile's Sarah Davis proves this point. When she stumbled upon the Chanel Cassette Tape bag, out of their Spring/Summer 2004 collection, which originally retailed for $1,600, she knew she had something special. "It's so hard to price pieces like that. We couldn't find a single prior sale to compare it to and ended up pricing it at $9,000. It was up for less than 30 minutes. I posted it on Instagram, and gone!"

That's better than any other investment I can think of! Which other kind can you enjoy by wearing daily and still gain value from in the long run? Not cars and not watches. And you certainly can't wear real estate or stocks. My first Birkin, purchased in 2002, cost me $4,500. I can sell it today for $12k (though I am saving it for my future granddaughter). I always say—Hermès bags make the best retirement fund!