There is no regulation when it comes to tipping in Dubai. Though it has been a custom to tip but it would still depend from your discretion whether to give or not.
Almost all major restaurants are charging 10% service charge (mandatory) and 6% government tourism fees on your bill. The service charge will not go directly to your waiter but is handled by the management and divided equally to all the staff of the establishment at the end of the month. But if you are happy with the service you may give tip to your waiter. This amount will not be divided to all the staff but to your waiter alone.
Tipping can be done via cash or card as part of your bill.
Other information on tips and service charge are available at the link below.