Generate ctags for rails project:
ctags -R `bundle show rails`/../*
C-] - go to definition
C-T - Jump back from the definition.
C-W C-] - Open the definition in a horizontal split
C-\ - Open the definition in a new tab
A-] - Open the definition in a vertical split
After the tags are generated. You can use the following keys to tag into and tag out of functions:
Ctrl-Left_MouseClick - Go to definition
Ctrl-Right_MouseClick - Jump back from definition