Greetings are short phrases that you can use to begin a conversation.

Getting their attention

Salut - equivalent to "Hi", or "Hey", and is chiefly used in an informal instance.
Bonjour - equivalent to "Hello" and "Good morning", and is used in formal scenarios.
Allô - also equivalent to "Hello", but is only used in telephony.
You can also add Monsieur (Mister), Madame (Missus), or Mademoiselle (Miss) to your sentence.

Examples

Salut, Madame! - Hey, Miss!
Bonjour, Monsieur - Good morning, sir!

Questions

Comment ça va? - How is it going?
Comment vas-tu? - How are you going?
Que fais-tu aujourd'hui? - What are you doing today?