I have 2 tips for my brides and formal clients.
Tip 1. Allow 2-3 weeks minimum for Alterations. Most dresses will need alterations and while the alteration may seem simple. They can often be very involved. See video below.
Tip 2. Add alterations to your dress budget. I advise my PJB babes to add at least $100 to their budget to achieve the perfect fit. Again, while you may think it's just a hem, dress with lace, multiple layers and beading require more time and attention to detail which means more money.