Trading with foreign countries is an activity that goes back for millennia in Arab societies. The foreigner coming to the Arab world to buy or to sell will have to observe the normal rules of supply and demand in dealing with his Arab counterpart and will have to be ready to drive a hard bargain. In order to create the best climate to do business, you need to understand some of the Rules of the Game.
“If you address someone in their native tongue, they are 10 times more likely to buy from you — whatever their competence in English.” (Financial Times)
Remember that in the 21st century the Arab counterpart will almost certainly know English and may well have graduated from Europe or the USA. With such people it is unlikely that you would negotiate entirely in Arabic until you have had many years practice of conducting business in Arabic. However, you have a priceless asset to hand if you know some Arabic. This is appreciated enormously since it indicates not only an understanding of the Arabic language and culture but an interest in Islam. (With Christian Arabs the appreciation for your taking the trouble to learn some Arabic will be just as great as with Muslims.)
Try to observe some basic principles, especially the proper use of titles. It is not such a complicated matter: ordinary politeness would require you to say ya sayyid sami (Mr Sami) or ya ustaadh sami (Mr Sami). These will take you a long way. If addressing a woman, ya sayyida nadiya (Madam Nadia) would be well received.
You will usually be addressed by Mr / Mrs followed by your first name. This may come as a surprise to be addressed in this way, but it is a perfectly polite way of showing respect.
You should always be ready to greet people in Arabic warmly, to enquire after their health and to express pleasure at the opportunity to meet your counterpart.
Equally, at parting you should be ready to say in Arabic how much you have enjoyed the meeting, with apologies for taking up their time, and express the hope that you will meet again.