One of the most common problems that I encounter in my work is a lack of understanding of what a hyphen is for, and a resulting inappropriate use of it.
In the most common situation in which there is an opportunity to use a hyphen, there is a noun and two adjectives. For example: silver-haired gentleman. Late-blooming flowers.
The hyphen is used to show more clearly the relationship between the noun and its accompanying adjectives.
In order to know whether to use a hyphen or not, you need to establish what these relationships are. There’s an easy way to do this.
For each adjective, ask yourself whether the adjective describes a quality of the noun, or is there to modify the other adjective.
EG: silver haired gentleman. In this case, we ask ourselves: Does the gentleman have hair (haired)? Yes, he does, so “haired” modifies the noun.
Is the gentleman silver? NO! He is not. It is the HAIR that is silver. Therefore, silver goes with haired, and a hyphen should be used (silver-haired).
In the second example, “late blooming flowers”, the same process is used. Do the flowers bloom? Yes, they do! So blooming modifies the noun. Are the flowers late? NO! It is their blooming that is late. Therefore, late goes with blooming, and a hyphen should be used.
There are some cases where this does not happen. Consider, for instance, “big strong man”. Is the man strong? Yes. Is the man big? YES! Therefore, you see, BOTH adjectives go with the noun. In this case you do not use a hyphen; they are two separate attributes and so each stands alone. Just separate them with a comma: “big, strong man”.
Ask yourself these questions every time you have two adjectives with a noun. After a while, it will become automatic and you won’t have to think about it.