You will usually find better exchange rates compared to other airports. 100 prior to leaving the airport for cabs, tips, etc.
Speaking of tips, most hotels and restaurants will automatically add the tip change to your bill.
It is very rare to find coins with a denomination below 25 fils and so they are not as commonly used.Hey Sunil here to discuss Dubai currency with you If you are going to Dubai or recently have moved there you must know at least the basics of the currency used in Dubai. I have several one dirham coins saved as well as at least one bill of every denomination.I find them exotic looking and the coins have a historic feel to them.You can find ATM machines in shopping malls hotels, inside banks and in the newer bus stands.I recommend always carrying some cash on you, especially if you like to shop in the local markets of Dubai (the souks).