To begin yoga, one need to have an interest in their own well being. Such interest creates enthusiasm. This enthusiasm should reflect in the ways one follows simple discipline such as balancing his/her That, vihar and vishranthi. That's food, activities (physical and mental) and Rest (sleep,relaxing)
Eat when you are hungry.
Have adequate sleep.
Accept your capacity or limits to do a task and respect your body.
So, these are the key essentials one acquires to start yoga abhyas.