I don’t like to get stuck with a very old version of browser, so I install a Firefox binary provided by Mozilla, not the one by Debian.

Make sure to download a 64-bit version (as I use amd64) from here. The tarball expands to a directory named firefox. For example:

$ cd /usr/local/src
$ sudo wget http://releases.mozilla.org/pub/mozilla.org/firefox/releases/latest/linux-x86_64/en-US/firefox-15.0.1.tar.bz2
$ sudo tar -xvjf firefox-15.0.1.tar.bz2
$ sudo mv firefox ..
$ cd /usr/local/bin
$ sudo ln -s ../firefox/firefox .

This makes firefox command available system-wide.

To install flash, do:

$ sudo aptitude install flashplugin-nonfree

To install Java plugin, do:

$ sudo aptitude install icedtea-7-plugin