How can you prevent bad oral hygiene?

Sometimes its the things you eat. For example you can eat garlic and brush your teeth, but still have bad breath due to the garlic.

Brushing teeth, showering, brushing hair, washing hands. From physiological point of view, oral hygiene is not merely aimed at dental and gum health. Oral hygiene practiced every morning, involving...

Yes.

by being honest with them and letting then know that youre not trying to embarrass them, but to help because you care.

yes you can, even if you are a very healthy person, you need to see a dentist to see if all is well with your gums and teeth, if not they will tell you how to correct it.