The swirly lines are from leafminers. They're gone.

The tiny holes are from flea beetles. Looks like those critters are gone also.

Neither damage shown is adequate to affect the plant's health.

Thanks!

What can be done to prevent these pesties from ever showing up in the first place?

Nothing. They're in the environment.

You can use neem oil(organic choice) but not when flowering.Or 7 dust but it is a pesticide. Both work but if they are not devouring the plant I would not worry about it.

My jalapeno plants have leaf damage like that, but they still produced peppers anyway. For some reason it was only the jalapeno plants that got this kind of damage as the other 7 to 8 varieties dont show any signs of this. I didnt use anything to treat them as it didnt seem to be bad enough to be killing the plant.