1. Buyer Beware: Watch the size.
There is nothing wrong with shopping the clearance rack or borrowing a dress from your favorite cousin, but be careful with sizing. It's always better to purchase or acquire a larger size so that the seamstress can easily and quickly alter the garment. When a dress is more than two sizes larger, it will need to be completely taken apart and reworked so that the dress fits well on the body. While you might save money in the beginning, you end up spending more in the long run on alterations.
2. Wear the proper undergarments.
You just finished your workout at the gym and figured this would be a good time for your dress fitting. Since you were short on time, you didn't stop home to pick up your wedding dress undergarments. No big deal? But it can be a problem because your sports bra will not fit under your wedding dress the same way as your wedding undergarments. There could be good chance that your fit would be off. Play it on the safe side and wear the proper undergarments.
3. Hemming and the proper length.
Similar to wearing your undergarments, make sure you bring the shoes you plan on using for your wedding day. The seamstress determines the hem based on heel height. Also, if you feel you might trip or have trouble walking in heels, then advise your seamstress to sew the hem about 1" from the floor instead of almost touching the floor.
4. How much will it cost?
Price will depend on a lot of factors, and it's the main reason that professional dressmakers will want to see you in person to provide the best quote. For example, if your wedding dress has beading, it's more labor intensive then a plain fabric wedding dress. Does it have any lace? Handsew lace appliqués will have to be carefully removed for a hem and sewn back on compared to hemming a lace fabric overlay. Make an appointment and let your seamstress meet you in person for your price quote.
5. Schedule more than one fitting.
As a bride to be, it gets tiring going from appointment to appointment. When scheduling your dress fittings, take into consideration that it should mean multiple trips to your seamstress. The first time, the seamstress will meet with you and discuss your wedding dress needs and pin the dress for adjustments. Next, you'll come back in and see how the alterations look, but it usually will need some more minor adjustments. Often your final fitting will be two weeks out from your wedding date so that you can see if you are satisfied with the final alterations before walking down the aisle.