Clauses in English have a "subject" and "finite verb" often followed by objects or various types of complement.
The finite verb is a phrase. It has tense so may be in past or present tense. It might be simple or formed with an auxilliary
Any other verbs in the clause must be non-finite.
Gerunds and present participles always end "-ing". There is a fair amount of overlap between gerunds and participles. Gerunds are when an "-ing" word is the subject, object or in some other postion which function like a noun, and participles are modifiers.
Past participles often end -ed, but some end -en and some are irregular. But you can look them up in verb lists.
Infinitives have the base form of the verb, often with the word "to" in front.
Things to watch out for: The continuous tense of the main verb phrase is formed from a "be" verb and the participle. The perfect tenses are formed from a "have" verb and a past partciple. The passive voice uses "be+ past participle"
So in these forms the participle forms part of the finite verb.
Also there are nouns and adjectives that end in -ing and -ed. They aren't verbs at all, even if they are related to the verbs.
So first split the sentence into [subject phrase], [verb phrase], and [objects etc]. The verb phrase must contain the finite verb.
Any other verbal forms must be non-finite.
If they end in -ing they are participle/gerunds
If they end in -ed or have the past particple form, they are past participles.
If they are don't end in -ing or have the past participle form, espcially if they start with "to", they are infinitives.
To apply this to some questions
THe main verbs
- [I] [like] [to read]
"Like" is the finite verb, "to read" is an infinitive
- [It] [is] [easy to find faults with others]
"is" is main verb, "to find" is an infintive
- [She] [doesn't like] [to do anything]
main finite verb is "doesn't like", "to do" is infinitive
- [The boys] [are decorating] [the room]
The main verb is the continuous form of the verb. There are no other verbs.
- [We all] [enjoy] [eating ice-cream in the summer]
main verb is "enjoy" "eating" is a participle/gerund, since it is the thing that we enjoy, it is more like a noun than a modifier, so lets call it a gerund.
- [Mother] [took out] [a crumpled letter from the drawer]
main verb is "took out". There are no other verbs (crumpled is an adjective, it is one of the adjectives that looks like a past participle)