When it comes to formal dresses, fit is everything. "You can splurge on a pricey dress, but if it's not altered properly it won't look any better than a gown that's a tenth of the cost," says Claudine Hamm, CEO of Alyce Paris. As you break out the measuring tape, here are seven key things to remember when it comes to formal dress alterations.

To take the stress out of formal dress alterations, it's best to buy your dress early, leaving plenty of time for fittings and tailoring. Buy a dress 2 months before the formal event if possible. Schedule a fitting 1 month before the event.  If you're making major changes to the design—reworking the corset or cups, for example, or accommodating weight loss, you need to let your tailor know!

Formal gown alterations can add up. Some salons charge per service ($225 to shorten your gown, $150 to resew seams, etc.) while others do a flat fee (around $500 to $700) that covers anything you'll need to make the dress fit you perfectly. Design changes can cost anywhere from $50 (to cut a sweetheart neckline) to a few hundred (to add lace or beading, reshape the silhouette, or change the fabric). Make sure you factor in these costs before you buy.

Never order a too-small dress as motivation, Hall says. Even if you're diligent about those kale smoothies, you can't predict how much you'll shrink—and it's easier to take a larger dress in than to let a smaller one out. Instead, consider a gown with structure. About 40 percent have built-in corsets, which can be easily tightened or loosened. And ask if the designer will build new cups if your bust size changes. (Some won't.) Can't find a corseted gown you love? Try an A line, which covers lingering pounds. 

In general, the slinkier the gown, the harder it is to fix the fit if you gain or lose weight.

When your tailor adjusts the hem, make sure to bring the shoes you'll wear at the wedding so you'll be the same height you will be on the big day. If you haven't picked out your wedding shoes yet, bring a pair with a height comparable to the shoes you imagine yourself wearing!

Rita Ertl, Monique Lhuillier's director of alterations, advises brides to aim for a hemline that gently grazes the ground. "With your hem grazing the floor, you will be able to walk, dance, and mingle with your guests," Ertl explains. The main thing is to make sure you won't trip on the dress. After the seamstress pins the dress hemline so that it grazes the ground, walk around the salon a bit in your shoes to make sure it's a comfortable length. As for any brides wondering if a grazing hemline will end up staining and ruining the dress, rest assured that no matter the length, the bottom of the gown is going to get a little dirty on the big day, but the stains will come out during the post-wedding preservation of the wedding dress. 

So don't worry about it!

Bring whatever undergarments you plan on wearing along with you to your fitting. We all know the difference Spanx or the right strapless bra can make. You want to wear exactly what you'll be wearing on your wedding day, including shapewear, for the best possible tailoring. And while jewelry, gloves, and other accessories might not change the fit of your wedding dress, they contribute to the overall look. For example, where your wedding necklace falls might influence where you want the neckline of your dress to sit.

It's always good to bring your mom or a friend with you to your dress fittings, just so you have an extra set of eyes. Bring someone with a great sense of style and an opinion you trust!