How to write drama script?  

The writer always needs to know some elements to the drama he wishes to write. He needs to know the characters, plot, setting, etc. but as for formatting it, generally the dialogue goes in the center of the page and the scene number goes on the left side of the page. Find a group of screenwriters in the community and inquire as to how they format their scripts.

There's an excellent place called scriptfrenzy.org where they have TONS of help on structuring all kinds of scripts. Check it out. Every April they have a script challenge where you have to write 100 pages in 30 days. It's really fun and everyone is a winner no matter if you hit the 100 pages or not. Their reasoning is that whatever you DO write that month is more than you perhaps would have written on your own. It's really fun and the people who run it are very nice and a lot of fun.

Have you tried Adobe Story or Celtx? Both are free and do the formatting for you. I use Celtx myself. I like it. It's simple, no nonsense and easy to use. It'll save it to PDF as well. I've got Adobe. I'll be honest I haven't played around with it much. I have several scripts started and I don't want to transfer them at this point into another program.
Hope that helps. :)