implementing different page layouts in a single theme

Hi,

Thank you very much for helping me learn Drupal.

I could manage to customize a Drupal theme to fit for website.
Now I have templates with different layouts. Some have two columns, some have three. I'm figuring out how can i implementing these layouts in single theme? I mean how can i display these pages with different layouts using a single theme. Header & footer are same but main content layout differs based on page as follow:
Template 1:
[HEADER ]
[LEFT][MAIN]
[FOOTER ]
Template 2:
[HEADER ]
[LEFT][MAIN][RIGHT]
[FOOTER ]

also there are sub sections in main part of templates...

I think one way to do this is may be adding / resizing div panels and control them via CSS, separate for each page. but i am not 100% sure how to do it in Drupal.

Can you please suggest me how can i implement this?
thanks,
-Navi