Probably the best way to get started is to grab an Emacs 24 pretest and use technomancy's Emacs Starter Kit: https://github.com/technomancy/emacs-starter-kit

Emacs 24 gives you a solid package manager, and the starter kit gives you a good solid spot to build on.

From there, install the packages you want. If you want haskell-mode, just M-x package-install [return] haskell-mode. Get the full package list with M-x package-list-packages.