I often move lines around in vim so I have created mappings to make this easier.
These map to ⌘-j for move down and ⌘-k for move up. Works in normal, insert, and visual modes.
nnoremap :m .+1==
nnoremap :m .-2==
inoremap :m .+1==gi
inoremap :m .-2==gi
vnoremap :m '>+1gv=gv
vnoremap :m 'gv=gv
I use MacVim so I have used D(⌘) for the modifier key. To use in terminal based vims, use a different modifier e.g.