Tipping & etiquette in Lebanon (Beirut)

Having been in Beirut for only a few days, I have already asked myself the following question several times: Should I be tipping this person? I give you some examples, and I am thankful for all guidelines given. Is there also a general rule on how much tip you leave in a café, a bar or a restaurant?

* at the supermarket: an employee is packing my groceries and carrying them to my car. Tip or no tip?
* in a public restroom: the person respnsible for the hygiene. Tip or no tip?
* the guard in a parking. Tip or no tip?

:)