Even though Switzerland is a very small country the mentality of the Swiss can vary from region to region. Swiss German people are usually very polite, but somewhat "shy" or "cold" and you will find they might not easily get into contact with you. The Swiss-French and Swiss-Italian feel more comfortable being approached, but don't expect the American "easy-contact" way. However, people will usually be polite and helpful. It also depends on whether you are in a big city or out in the country. And since many Swiss people travel all over the world you will surely find someone that can speak English well enough to assist you. 

In all parts of the country it is considered polite to greet shop assistants as you enter a shop with and to thank them and say goodbye and thank you as you leave.

Since four different languages are spoken depending on the region you are in you would say  "Danke" for "Thank you" in German,  " Merci" in French and "Grazie" in Italian. There are also many English words that have made it into everyday expressions. And if you cannot remember the appropriate word in the local language just smile and say thank you and goodbye in English!

The Swiss like to go hiking or just for an afternoon walk and It is common to greet one another in German:  Grüezi , in French:  "Bonjour" and in Italian: "Buongiorno". It is not common to do the same in the cities.  

In the Swiss German part there are quite a few different ways to say goodbye depending upon whether or not you are formal or informal with the person. Some of them are "Adieu" or "Aufwiedersehen". "Ciao" is considered informal.  In the French speaking part one normally says "Au revoir" but in some regions some French speaking people will say "Adieu".  In the French part it is also polite to say "Madame" or "Monsieur" when thanking someone or when saying hello or goodbye.