Many objects have their own collective noun, so you should start by trying to find and use that. Some are well known e.g. A murder of crows, a flock of sheep, a pride of lions, and some are obscure e.g. A dole of doves.

For objects where you don't know what their specific collective noun is, there are nouns which are well understood in broader uses, I've mentioned some below and their common areas of usage.

For all: Group, Collection, Multitude

 

For animals: Shoal (fish), Flock (birds), Swarm/Nest (insects)

 

For plants: Clump, Cluster

 

For non-discrete entities (water, earth etc): Body, Mass

Many objects have their own collective noun, so you should start by trying to find and use that. Some are well known e.g. A murder of crows, a flock of sheep, a pride of lions, and some are obscure e.g. A dole of doves.

For objects where you don't know what their specific collective noun is, there are nouns which are well understood in broader uses, I've mentioned some below and their common areas of usage.

For all: Group, Collection, Multitude

For animals: Shoal (fish), Flock (birds), Swarm/Nest (insects)

For plants: Clump, Cluster

For non-discrete entities (water, earth etc): Body, Mass