The most basic French words required for any visit are those of greeting and goodbye: "Bonjour" and "Au revoir". Informal alternatives may also be used, depending on the person who is being spoken to.
"Salut" is frequently used between friends and youths as an alternative to the more formal "Bonjour," which is better used by children speaking to adults, or adults speaking to adults.
French speakers may kiss each other on the cheeks when greeting one another, but only between friends or family, and hardly ever on formal occasions. The number of kisses varies between regions of France, from two to four times. Depending on the specific region and the level of the friendship, females may be seen kissing females and males kissing males. Visitors are not necessarily expected to follow this custom, and are unlikely to have close enough friends to do this with, at least at first.
To make more friends, the phrase "Comment vous appellez-vous?" translates literally as "How do you call yourself?" It's used to ask a new acquaintance for a name, and it is structured in the appropriate formal mode. To give a name, use "Je m'appelle...," which literally translates as "I call myself..."
To ask how a person is doing, try "Ça va?" This is an informal structure, but is unlikely to be seen as rude as it is a friendly enquiry. "Comment allez-vous?" is the formal alternative. Listen out for the words "bien," "mal," "trés bien" or "trés mal" in the response. These mean good, bad, very good and very bad respectively, and will give an idea of the speaker's wellbeing.
It's also always good to know how to say "thank you," in this case, "Merci," or "Merci bien."