Table control

Hi

I am new to ABAP. I have a few doubts on table COntrol.I am in search of the Best Practises to be followed.

1) Should we always map the Table control to a Structure or an Internal table.

2) Whenever i key in Data for a line in Table control and hit enter key, the contents vanish.

Can anyone send me a Template of the source code of how it needs to be handled.