It's easy to teach on italki, by Skype etc.
I would suggest you start by always writing in a good grammatical style. This will encourage students to do the same. So, "How can I become a teacher?" is better than "how can I become a teacher"
If YOU forget capitals, question marks, and full stops/periods, then the students will think it's okay for them to forget them too! Some need to pass exams, and they need good examples to follow.