Another grammar point that goes with gerunds is using infinitives (ex. to sleep). The big question is, when do you use an infinitive and when do you use a gerund??? There are lots of rules and cases where you use one or the other, for this post, I will give an overview and go into more detail in future posts.
Both gerunds and infinitives can be used as the subject of a sentence:
Surfing at the beach is fun.
To surf at the beach is fun.

Both can be used as the object of a sentence:
I like surfing at the beach.
I like to surf at the beach.

Only gerunds can be used as the object of the preposition:
I like speaking about surfing at the beach. – correct
I like speaking about to surf at the beach. – incorrect

Here are a few generalizations when deciding to use one or the other:

Gerunds are used when the actions are finished or they are real.
I finished surfing.
I stopped surfing.
(I have completely finished surfing.)

Infinitives are used when the actions take place in the future or they are not real.
I stopped to surf.
(This means I was doing something else, like walking and I stopped doing that and then soon I will begin to surf.)