Gerund as Noun (Gerund Phrase)

What is a gerund phrase? Though the term might sound a bit intimidating, it really is simple. Here, we’ll take a close look at gerund phrases and provide several examples so you can easily recognize them and use them to create interesting sentences.

Decoding the Gerund Phrase
Time for a quick refresher: A gerund is a noun formed with a verb ending in -ing. Words like swimming, tying, dreaming, eating, fishing, and drinking can all be used as gerunds.

Now that we’ve refreshed your memory, let’s take a look at the gerund phrase. A gerund phrase always follows these rules:
-Gerund phrases always start with gerunds
-Gerund phrases always include modifiers and often include other objects
-A gerund phrase always functions as a noun
-Gerund phrases are always subjects, objects, or subject complements in sentences.[1]

The gerund looks exactly the same as a present participle (verb with -ing ending also used in the Present Progressive Tense), but it is useful to understand the difference between the two. The gerund always has the same function as a noun (although it looks like a verb). Some uses of the gerund are covered on this entry.

THE GERUND AS THE SUBJECT OF THE SENTENCE

EXAMPLES
Hunting tigers is dangerous.
Flying makes me nervous.
Brushing your teeth is important.
Smoking causes lung cancer.

THE GERUND AS THE COMPLEMENT OF THE VERB 'TO BE'

EXAMPLES
One of his duties is attending meetings.
The hardest thing about learning English is understanding the gerund.
One of life's pleasures is having breakfast in bed.

THE GERUND AFTER PREPOSITIONS
The gerund must be used when a verb comes after a preposition. This is also true of certain expressions ending in a preposition, for example the expressions in spite of & there's no point in.

EXAMPLES
Can you sneeze without opening your mouth?
She is good at painting.
She avoided him by walking on the opposite side of the road.
We arrived in Madrid after driving all night.
There's no point in waiting.
In spite of missing the train, we arrived on time.

THE GERUND AFTER PHRASAL VERBS
Phrasal verbs are composed of a verb + preposition or adverb.

EXAMPLES
When will you give up smoking?
She always puts off going to the dentist.
He kept on asking for money.

There are some phrasal verbs that include the word "to" as a preposition for example to look forward to, to take to, to be accustomed to, to get around to, & to be used to. It is important to recognise that the word "to" is a preposition in these cases because it must be followed by a gerund. It is not part of the infinitive form of the verb. You can check whether "to" is a preposition or part of the infinitive. If you can put the pronoun "it" after the word "to" and form a meaningful sentence, then the word "to" is a preposition and must be followed by a gerund.

EXAMPLES
I look forward to hearing from you soon.
I look forward to it.
I am used to waiting for buses.
I am used to it.
When will you get around to mowing the grass?
When will you get around to it?

THE GERUND IN COMPOUND NOUNS
In compound nouns using the gerund, it is clear that the meaning is that of a noun, not of a continuous  (present progressive) verb. For example, with the word "swimming pool" it is a pool for swimming in, it is not a pool that is swimming.

EXAMPLES
I am giving Sally a driving lesson.
They have a swimming pool in their back yard.
I bought some new running shoes.

THE GERUND AFTER SOME EXPRESSIONS
The gerund is necessary after the expressions can't help, can't stand, to be worth, & it's no use.

EXAMPLES
She couldn't help falling in love with him.
I can't stand being stuck in traffic jams.
It's no use trying to escape. [2]

taken from:

[1] http://www.gingersoftware.com/content/grammar-rules/nouns/gerund-phrase/

[2] http://www.edufind.com/english-grammar/gerund/