au! BufRead,BufNewFile * lcd %:p:h
This makes it so that when you open a buffer, you cd to the current directory (only for that window), so you can quickly open files in that directory.
[% is the current file relative to pwd, :p converts to a full path, :h takes off a path component, lcd does a cd but only for the current window]
Another tip is that when your internet connection sucks enough for SSH lag (tethered, free wifi, whatever), you can edit a file locally and have vim do the SCP back when you write:
" Allow easy navigation to relative files
cmap %/ %:p:h/
Thanks for the laggy SSH tip.