A ‣ People 
Collective nouns are used to describe a group of the same people or things.
B ‣ Words associated with certain animals 
A flock of sheep or birds, e.g. geese/pigeons; a herd of cows, deer, goats; a shoal of fish (or any particular fish, e.g. a shoal of herring/mackerel -note the use of singular here); a swarm /swɔ:m/ of insects (typically flying ones, e.g. a swarm of bees/gnats).
A pack of ... can be used for dogs, hyenas, wolves, etc. as well as for (playing) cards.
C ‣ People involved in the same job/activity 
These nouns are used with singular or plural verbs, depending on your point of view.
A team of experts/reporters/scientists/rescue workers was/were at the scene of the disaster.
The crew was/were saved when the ship sank. [workers on a ship/ambulance/plane]
The company is/are rehearsing a new production. [group of actors]
The cast is/are all amateurs. [actors in a film or theatre production]
The public has/have a right to know the truth. [the people as a whole]
The staff are on strike. (normally used with a plural verb; general word for groups who share a place of work, e.g. teachers in a school, people in an office)
D ‣ Physical features of landscapes 
In the picture we can see a row of cottages near a clump of trees with a range of hills in the background. Out on the lake there is a small group of islands.

E ‣ Things in general 
a pair of birds sitting on a branch [ two of anything that are the same]
a couple of strawberries [vague way of saying two, not necessarily exactly the same]
a pile/heap of papers (or clothes, dishes, toys, etc.)
a bunch of flowers (or grapes, bananas, etc.)
a stack of chairs (or tables, boxes, logs, etc.)
a set of tools ( or pots and pans, dishes, etc.)