Abu Dhabi is welcoming to visitors, but a little cultural awareness goes a long way toward being a genuinely respectful guest.
Outside religious and government sites, dress in Abu Dhabi is more relaxed than many visitors expect — smart casual is fine in malls, hotels and restaurants. That said, overly revealing clothing in public spaces (as opposed to resort pools and beaches) is best avoided out of general respect, and religious sites like Sheikh Zayed Grand Mosque have specific, stricter requirements.
Public displays of affection beyond hand-holding are best kept minimal. Alcohol is only consumed in licensed venues (hotels, licensed restaurants and clubs), never in public spaces or while visibly intoxicated in public. Photographing local people, especially women, without asking first is considered impolite.
A handshake is a common and appropriate greeting in most business and casual contexts; some Emirati women may prefer not to shake hands with men they don't know, in which case a polite nod or verbal greeting works fine. Using your right hand for eating, giving and receiving items is customary.