You've decided to shop online for your wedding dress.  Perhaps you fancy a vintage style, like you've seen in your mother's photo albums, and you can't find it in today's collections.  Perhaps you're looking for specific features, like short sleeves or a cathedral-length train, that are hard to find in your local high street.  Perhaps you've fallen in love with a Vera Wang gown but not with its price tag.  Or perhaps you can't wait the five or six months most dress shops will require for your order to be processed.

Whether you are driven by passion or practicality, you've got a lot of work ahead to find the right gown for you.  And to make it all the more challenging, with an online purchase, you won't actually be able to get your hands on the dress until you've already paid for it.  Consider these points to help make your decision a great one.

1. Determine your budget.

If you have a limited amount of money to spend, keep in mind the cost of alterations.  Any wedding gown--new or previously worn--will be most flattering when it is tailored to fit your frame, and for most brides, wearing the dress straight out of the box it arrives in will not be an option.  At a minimum, it's likely that your dress will need to be hemmed to the right length.  Dresses with trains will also need a bustle, which rearranges the extra fabric to just above the floor so that you can move about easily at your reception; you may need a seamstress to add (or reinforce) the bustle loops and hooks or buttons.  Your local bridal shop can recommend a seamstress who is accustomed to working with wedding gowns.

And naturally there's more to dressing up than simply the dress.  Consider which of these you will also need to purchase: tiara, headband or combs; veil; necklace, earrings or other jewellery; gloves; hosiery; undergarments and petticoats; shoes.  All of these will contribute to the overall cost and should play a role in your budget.  Anything you can borrow from someone special will lend more meaning to your outfit and give you a bit more money to spend elsewhere!

2. Decide how much you're willing to compromise.

Do you dread the thought of turning over any aspect of wedding planning to anyone else--even your future husband, your best friend or your mother?  If so, avoid making trade-offs on any part of your dress.  At first you may think you are willing to live with a particular gown's ho-hum neckline to get its fantastic bodice work, but it's the ho-hum bit you will still be thinking about years later.  Your wedding day is not a day to have regrets about, so be realistic about how perfect your perfect dress really needs to be.

3. Spend some time trying on dresses in person.

There is no substitute for surrounding yourself with a variety of shapes, styles, colours and fabrics--and for getting a trusted opinion on how you look in them.

Shapes

The shape or silhouette of the dress will have the most impact on whether it suits you.  What you choose should depend on your body's proportions.  Empire waists are better for the smaller chested; straight or column dresses are for the tall and slender-hipped.  When in doubt, an A-line will flatter anyone.

A comfort factor to consider is sleeves.  Sleeveless dresses are the most common but may leave you feeling exposed, especially if there are no straps.  Dresses with sleeves will hide flabby upper arms, but the fabric may make it impossible for you to raise your arms, making dancing or even hugging guests a challenge.  Sleeves will also impact how you accessorise, so keep that in mind if you are keen on wearing opera-length gloves or your grandmother's stunning pearl bracelet.

As for the train, the general rule is that the longer the train, the more formal the dress.  This is really only a consideration for the ceremony itself since afterwards you can either bustle it or--with a few rare styles of dress--remove it altogether.

Fabrics

Wedding gowns are available in a range of fabrics, each with their own lustre, feel and weight.  Silk and satin are most common; silk is the more expensive of the two, and high quality lace is probably as expensive as it gets.  Try a few different fabrics to see if you are passionate about one in particular; if not, don't let it influence your decision.  No matter what fabric you wear on your wedding day, you will be the best dressed woman in the room.

Colours

Most brides will choose white or some form of off-white (ivory, eggshell, cream), but there are also non-traditional colours.  Try on dresses of different colours and get the shopkeeper's impression: when you enter the room, is their eye drawn to you, or the dress?  The idea is for you to look great in the dress, not for the dress to look great on you.

If you truly can't get to the shops, try putting on a white or cream t-shirt, or drape yourself in a bed sheet, and look in the mirror.  Does it make you look washed out, or give you a healthy glow?  Or consider your day-to-day jewellery.  Do you prefer gold (which complements off-white) or silver and platinum (which complement pure white)?

Styles

When it comes to style, bear in mind whether the gown you choose fits with the feel of the overall event.  You’ll want a different dress for a beachfront wedding than for a black-tie ballroom affair.  Beyond that, look at photos in bridal magazines and see what appeals to you, bearing in mind that you may actually want more bling (beading, jewels, sequins) than suits your normal comfort level.  Also note that if you have a particular necklace or other jewellery in mind, you will want to choose a neckline to accommodate. 
While you're in the shop, look at the price tags.  It will prepare you in case there's any doubt of whether a particular dress online is overpriced.

4.  Do your online search.

You've gathered details on the colour, shapes and styles that are right for you.  These all make great search terms to help you find the perfect dress.  Now the trap to avoid is size.

Unfortunately, wedding dresses seem to be more inconsistently sized than any other clothing item you will ever buy.  This inconsistency is magnified if you are considering a previously worn dress that the owner before you may have already altered.  For these reasons, measurements (bust, waist, hips, and length) will be much more reliable than sizes; if they are not explicitly stated, ask the seller.

Since a perfect match for your measurements is unlikely, err on the side of getting a dress that's too large.  You can always have the dress taken in to fit you, but it's far more difficult to get good results if you need to add room. At the same time, there's only so much fabric that can easily be taken away without major reconstruction, so don't go too big, or the alterations may end up changing the look of the dress--particularly if there are embroidery or beading patterns that might be interrupted if fabric is removed or seams are adjusted.

5. Contact the seller to get more information.

First of all, make sure you are getting exactly what you expect.  If specific features of the dress are important to you, ask for more details, or better yet, photographs.

Confirm that the dress, if previously worn, has been cleaned and that the photographs are from after the cleaning.  If the cleaning process damages the dress, or leaves behind stains the seller thought would come out, you want to know that before you're out a few hundred quid.

Find out whether the seller accepts returns and, if so, what the conditions are.  If you've got multiple dresses in mind and upfront cost is not an obstacle, you might consider buying more than one and returning (or reselling!) the ones you don't use.

6. Buy!

You've scrutinised it from every possible angle, and it's met all your criteria.  So ask yourself one final question: Do you love it?  If the answer is yes, start bidding!