The language of daily communication is English.
Dubai is a Muslim country. There are mosques dotted all over the city, and they all have minarets from which the call to pray can be heard five times a day. Because the call is amplified, it can be surprisingly loud especially in the early morning. In the summer, as the pray call begins before dawn, it can be very early. Most Westerners get used to the call and can sleep through it, but it takes time for light sleepers. Eventually, it becomes part of the life in Dubai.
Almost from the moment you arrive in Dubai, you will see men immaculately dressed in white dishdasha or khandoura (rather like a floor length shirt) and women in abaya and hijabs (black gown and head scarf). This is national dress. There are small variations within the GCC, but it is all variations on a theme. Emiratis are very proud to wear their national dress. The women may have expensive designer outfits on under their black gowns, but they present a perfectly groomed and modest appearance to the world. Very few women wear the niqab (full face covering), but it is worn by the more conservative Muslims.
Along with traditional Arab clothing you will see various traditional Indian and Pakistani outfits, men wearing identifiably Afghani dress and very occasionally, different types of African dress. This is all part of the richness of living in a multi-cultural country. Unfortunately, it has become commonplace for me. I would love to experience it all again as a newcomer will, with surprise and wonder.
Apart from visual differences, there is the weather. Get used to being hot all the time in the summer. Of course, air-conditioning takes the sting out of the summer, but it is lurking outside heating up your car even when parked in an underground car park. The upside is that the winter is like a six month long summer in most other countries. So do not despair.
Bureaucracy is a beast in all countries and Dubai is no different, but it is trying harder to minimize the issue. Nevertheless, get used to needing copies of a few standard items to do or apply for almost anything. Almost nothing can be done in Dubai without a swatch of photos – get 24 passport photos before you leave home and you will always have plenty; of course, if you have a family, they will need at least 12 photos each, too. The other top requirements are a photocopy of your passport, your residence visa (once you have one), your salary certificate, and your Emirates ID card (once you have that). Clearly, getting your residence visa and then your ID card are the first hurdles and cannot be done without the help of your employer.
While it is possible for a couple to both have work visas if both are working, the way it usually works is that one has the residence visa and the other has a spousal visa. It is possible for someone on a spousal visa to work, but that person will need a letter of no objection from the resident.
Find the fun in the unexpected and avoid culture shock.