What is the difference between them and when I should use -ing form and when -to+infinitive in similar cases?
"I could see her eyes starting to tear up."
or
"I could see her eyes to start to tear up."
It's always difficult for me to differentiate these two type of expressions.
Best Answer
Particular verbs (and adjectives) take particular kinds of complement, and there are few general rules.
Verbs of perception such see, hear, and feel, can take:
But they cannot take a to infinitive clause: not I saw her eyes to start to tear up.
Other words have different patterns: know can take a that clause, and a to infinitive clause, but not the other two kinds. (There's a special context where know in the perfect can take an infinitive clause without to: I have known him go there; but otherwise it can't), Understand can take a that clause, a to clause, or a gerund clause, but not an infinitive clause without to.
For the most part, you just have to learn what complements a particular word takes.