Use simple courtesy with your client. Address them formally unless they request otherwise. Open and close the car door for them. Before leaving the initial departure point, confirm the arrival address and any other departure times with the client to avoid any mix-ups. It is a good idea to carry business cards with you that include a phone number where you can be reached in case your client needs you during the engagement.
As a courtesy and thank you for a job well done, many of your clients will offer you a tip. It is important to remember that while tipping is customary with some countries and some companies, it is not with others. Consult your company on their policy concerning tipping. Remember that even if your client does not tip you, it does not necessarily mean that they were dissatisfied with your service, just that they may not be accustomed to it. If a client gives you feedback, respond politely and privately consider their comments in order to help improve your experience with future clients.
No matter who your client is or how long they have engaged your services, a main tenet of limousine driver etiquette requires that you maintain a certain degree of silence concerning their actions or conversations while in your presence. Of course if your client engages in illegal activities you should report it to the appropriate authorities, however any personal details or actions of your client should remain private. Keeping the confidence of your client will help lead to future business.
