Commas!

I have to admit, for me commas are still a tricky matter sometimes. Although I feel like having learned it for a hundred times, there are still the same questions: is there supposed to be a comma or certainly not? Is it similar as in other languages such as German? I want to get to the bottom of the basic rules- again J

Numbers	comma: 7,009,826 NO comma:  $3.40 comma: September 1, 1998 NO comma: September 1998
Salutations	“Stephanie, can you help me please?” Dear David,
Geographic places	Machu Picchu, Peru, is one of the most famous sites in Latin America. She lives in Mariahilferstraße, Vienna, Austria.
Please	comma: “Call me, please.” NO comma: “Please call me.”
Affirmatives, Negatives and Question Tags	No, I am not. You can speak Spanish, can you? So it’s all my fault, is it?
Adjectives	It was a long, exhausting day. They served some salty, spicy snacks.
Adverbs	after nevertheless, however, moreover, etc.: However, the exam was easy for her. The exam, however, was easy for her.
Enumerations	Today I went to university, did my homework, studied and started reading a new book.
Between Main Clauses	Between two main clauses which are separated by and or but: I went home, and prepared lunch for my family. To separate parts of a sentence: I went home, locked the door, took off my shoes, put off my jacket and started preparing lunch for my family.
Conditional Sentences	comma: When I will go to Spain, I will visit my friends. NO comma: I will visit my friends when I will go to Spain.
Direct Speech	comma: She said,” I cooked dinner for you.” NO comma: “Did you cook dinner?” I asked.
Introductory Clauses	In summer, I will go on holiday. After going on a sight-seeing tour, we will go to the beach.
Additional Information	Vicky, my sister, is 6 years younger than my brother.
Opposites	Sucre, not La Paz, is the capital of Bolivia.

I guess this is pretty much it. Of course, there are always some exceptions, but my intention was to give a short overview for remembering the basic rules.