In some cases there is a change in meaning depending on whether the verb is followed by the gerund or the infinitive. Let’s consider the most important verb patterns:

Stop

Stop to do something – stop doing one thing and start something different.
Stop doing something – stop the thing you are doing now.

e. g.

He stopped having lunch. (means he did not continue to eat his lunch, he finished  eating)

He stopped to have lunch. (means he finished one thing in order to have lunch then)

When I came into work this morning I met my boss and stopped to ask him about a pay rise.

I’ve stopped asking my boss for a pay rise. It’s a waste of time, he just keeps telling me he’ll think about it.

Remember/forget

We use remember/forget to do for necessary actions. The remembering is before the action.

We use remember/forget doing for memories of the past. The action is before the remembering.

e.g.

I must remember to post this letter today. It’s important.

I can remember posting the letter. I posted it on Friday morning.

The clothes are still dirty because I forgot to switch on the machine.

I’ll never forget flying over the Grand Canyon. It was wonderful.

Try

Try to do something (I don’t know if it’s possible) means to attempt something, to do one’s best

Try doing something (I want to solve a problem) means to do something which might solve the problem

e.g.

I’m going to try to find a new job. (I might not be able to find a job)

A: My job doesn’t pay very well.

B: Why don’t you try finding a new job? (You might earn more money, if you get a new job)

I’m trying to run this computer program.

I tried clicking on the box, but it doesn’t work.

Regret

Regret to do something means to be sorry for something you are doing, e.g. giving bad news.

Regret doing something means to be sorry because of something that happened in the past.

e. g.

We regret to inform you that we are not taking on any new staff at present.

I regret spending all that money. I’ve got none left.