How to effectively work with multiple files in Vim?

Why not use tabs (introduced in Vim 7)? You can switch between tabs with :tabn and :tabp, With :tabe <filepath> you can add a new tab; and with a regular :q or :wq you close a tab. If you map :tabn and :tabp to your F7/F8 keys you can easily switch between files.

If there are not that many files or you don't have Vim 7 you can also split your screen in multiple files: :sp <filepath>. Then you can switch between splitscreens with Ctrl+W and then an arrow key in the direction you want to move (or instead of arrow keys, w for next and W for previous splitscreen)