I think that we can't seperate theory from practice.
Both of them complete each other.
Teacher should have a theoretical background before practising teaching.
This will help him/her select what is suitable for his/her students.
For Krashen & Vygotsky, they are very great linguists for me.
They called for very applicable theories and I used them in my classroom.
Krashen called for creating some sort of naive environment
and we need this theory nowadays very much.
He thought that we can transfer this environment to our EFL classrooms
through reading and listening to the English Language
This approach is called the Natural Approach.
For Vygotsky, he thought that students can learn from each other
What they do cooperatively, they can do alone later.
Actually, through theortical background, you can mix many approaches
and creat your own.
I like very much to culture my mind before starting
to create my own from my experience.
This makes me look at the strengthes and weakenesses
of those linguists' viewpoints,
and then adopt those are good and
adapt those are not suitable for my EFL students.