If you're ordering a mermaid style dress, consider sending them additional measurements like how far down from the hip you want the flare to start and how tight you want it to be at that point (how many inches around). Sending pictures back and
forth is not that efficient.
Also, if you are getting lace (or beading) added, ask them to send you pics of it overlaid on the dress before they sew it on. I approved a picture of some lace but when they sent me pictures of it on my final dress, I realized they'd picked a
different color than what I had approved (same pattern) and it clashed. I could have told them immediately that I wanted the lighter color if I would have just seen it laid against my dress.
Because I didn't clarify these points, I had to ask for my dress to be changed a few times, which of course means that I am receiving it behind schedule, so I agree with everyone who said order early.
Good luck! Overall, I have been happy with my experience. I haven't actually received my dress yet, but from the pictures, I'm quite impressed with how it turned out.