The -ing form of a verb is called "the gerund". There are just three rules of using the gerund:
Examples:
Eating outside makes me feel good. (subject of the sentence)
Swimming is always a pleasure for me. (subject of the sentence)
Studying English is very popular in Vietnam. (subject of the sentence)
Smoking is bad for your health. (subject of the sentence)
Examples:
Have you finished studying the gerund? (after some verbs)
I enjoy reading in bed. (after some verbs)
I dislike having dinner with my wife’s family. (after some verbs)
I feel like singing. (after some verbs)
I have just finished cleaning the house. (after some verbs)
He keeps on talking in the class. (after some verbs)
I don’t mind helping him. (after some verbs)
I practice speaking English every day. (after some verbs)
My wife spends hours talking on the phone. (after some verbs)
I hate going to school. (after some verbs)
I like having lunch in the garden. (after some verbs)
I love waking up on a sunny morning. (after some verbs)
I started building this house last year. (after some verbs)
Hey, please stop talking. (after some verbs)
Examples:
I am thinking of buying a bigger house. (after prepositions)
He left without saying good bye. (after prepositions)
Note:
“Help” can be used with the infinitive and base form with no difference in meaning. (Example: He helped me to move vs. He helped me move)
“Start” can be use with both infinitive and verb + ing with no difference in meaning. (Example: It started raining vs. It started to rain)
“Try”, “remember”, and “stop” (“stop” with infinitive) can be used with infinitive form and verb + ing but the meaning is different.
“Hate”, “like” and “love” can be used with the infinitive and verb +ing with no difference in meaning. (Example: I like to play tennis vs. I like playing tennis)