Emacs - how do I automatically enter minor modes when I enter a major mode?

I'm kind of a newb when it comes to emacs. I know about the .emacs file but have very little idea as to do anything more advanced than elementary stuff.

Whenever I enter latex-mode, I'd also like to automatically turn on flyspell-mode, reftex-mode, auto-fill-mode, and also set fill-column to 120. How do I edit my .emacs file to do this?

Thanks!

(add-hook 'latex-mode-hook
    (function (lambda ()
       (flymake-mode)
       (reftex-mode)
       (auto-fill-mode)
       (setq fill-column 120))))

for example should work.

You can set a so-called hook to a major mode. Have a look at this page of the manual for some examples.