Great topic Julien. And very involved here. First is that it depends where you are working, how big is the company, who owns it, where are they from, what is the industry etc. It is not cut and dried.
How you behave will very much depend on a number of factors - your position. This culture is very class conscious. You are always expected to be friendly and approachable but not too much. It is similar to walking into a restaurant when you arrive at work - you say hello to everyone, even if you do not know them! And it does not matter if you just saw them in the parking lot, you still greet them again on arrival!
Dress code- again depends on what you are doing and your position. Things here are somewhat different then many other countries, just watch the news programming to see what I mean. I often wonder if the announcers are there to do a job or look for a boyfriend! The standards are very different and you will need to see what is appropriate where you are. My personal standard is always classic, simple no matter where I am working. IF it is a very casual environment, good quality jeans and a classic tshirt. More office oriented - dress pants and a simple top and jacket or sweater.
Body language here is all over the place. Good luck with that one! Seriously - keep your head down, watch and learn is my motto.
Culture here is very very social. It can be tough to adapt to and really tough to manage if you are at that level.
Time - well there is little respect for time or the value of time. Fundamentally most are underpaid so they see no value in their time. It is a tough one to deal with. IF you are in management it is a huge deal to handle lateness, not showing up etc etc. Do not expect your appointments to show up on time and do not expect to be received on time. Always be prepared with something to do or read. Again my personal take: my time has value, I will give you 10 minutes then I am saying something. 10 more minutes and I leave. If you have not arrived withing your 20 minutes and not called or messaged me, I am on to the next thing. I believe this is a huge issue in this country! But that is me.
Negotiation: Dominicans do business with people they know, people referred to them and often people they like. Do not expect to be taken seriously the first while you are here. Unless you are brought in by an established company, it will take you a couple years to be accepted. That is because many expats come and go. Dominicans do not believe you are staying until you have been here long enough to convince them!
It is very much about who you know. You need to build a network of people. BUT be very careful who that is, you are judged by who you associate with! It will take time to know who is who.......