It can be challenging to identify students who would do well online. There are several self-assessment quizzes online that some schools require students to take; e.g. Will you be a successful online student?, How will I know if I'm ready to take courses online?
The students should be computer literate and have access to a computer outside of class--whether it be at home or a school-sponsored lab.
Explaining to older students that keyboarding is very similar to typing can sometimes reduce their anxiety. Cohort groups of peers working together can also provide wonderful support.