I'm no expert, but I've been hitting up the Dominican salon for a year and here's what I've learned:
DO:
Be very exact with what you want; because they will do suggestive styling, i.e. what they think your hair needs, like extreme heat and saying the word "relaxer" every ten minutes if you're stretching.
Be prepared for the heat of a thousand suns on your head if your roots aren't freshly relaxed. And it hurts like h*ll!
Be sure to tell the, to use a deep conditioner, many of them shampoo and go; not good for anybody's hair.
Do get ready to wait inbetween services: at my salon, they work on fifteen girls at once; it's a race to the five dryers and the seven chairs!
DON'T:
Let her set the dryer heat to H*LL...make sure to tell her to keep it low to medium, because that dryer is a killer
Be afraid to bring in your own shampoo and conditioner; I do and she is not offended at all, it's just better than the generic "One-size-fits-all" shampoo they use, which tends to be drying.
And finally, don't let just anybody slap that relaxer in your hair! From my personal experience at over seven different Dominican salons (I was looking for a good fix), and listening to some of the women who have frequented them for years, not all Dominican women are equipped to put the chemical relaxers in hair.
That's all I can think of...I've had great Dominican salon experiences, and you will too.