1) between two or more items in list of words:

Red, pink, yellow and white roses filled the huge vases

Нужно ли тут ставить запятую перед and? В учебнике Дроздовой не ставится, но в интернете много где находила сведений о том, что ставить таки стоит...

2) after a subordinate adverbial clause, after a phrase which comes before the main clause, after long clauses and phrases:

a) When the sun is shining brightly above, the wprld seems a happier place.

b)In the summer of 1987, many trees died.

Long-это насколько длинное? Всё условно?

3) After non-finite or verbless clause, at the beginning of a sentense:

a) To get there on time, she left half and hour earlu

b) Happy and contened, the cat felt asleep

4)To separate: therefore, however, by the way, for instance, in fact, yes, no, of course, on the contrary, o the other hand, consequently, furthermore, moreover, nevertheless, in the first place, firctly, unfortunatelly.

5) Before&after any element, which interrupts the phrase:

The fire, although it had been burning for several hours, will still blazing fiercely.

6)"extra information"

Queen Elizabeth II, who is very popular monarch, celebrated her Silver Jubilee in 1977

Сравните: The hills that seprate Lancashire from Yorkshire are calles Pennies 

7) Between main clauses linked by a conjunction (and, as, but, for, or), esp. when the first clause is long:

We had been loking forward to meeting Ann's husband, but discovered he was not as pleasant as we hoped.

8) before as, for, since meaning "because"

9)после званий, титулов

10)при написании дат, год отделяется от месяца и числа.

11) выделяются деепричастные обороты:

Seeng the dog approaching, he ran off down the street.

12) обращения выделяются запятой 

13) Устойчивая форма официального письма:

Dear Sir or Madame,

...

I look forward to hearing from you,

Yours faithfully,

Name.