infinitive and gerund confusion

English as a Second Language English Vocabulary, Grammar and Idioms
1

Sometime, I cannot understand whether gerund or infinitive will be the right form of a verb in a sentence.

For example:

The key to being (or to be) healthy lies in being physically active

or

The first step to being …lies in being physically active

pls suggest

2

I suggest ‘being’. ‘To’ is a preposition there, not the infinitive particle.

3

Could you please explain sir…We do say the first step to reduce pollution…so why not here be…please help me

4

You can usually say either, but the gerund is more careful.