The simplest way occurs by default if you run Vim in nocompatible mode (which is the default if you have a vimrc). Simply by including the proper text in your 'viminfo' option or leaving the nocompatible default alone, Vim will automatically write all your registers to a file and restore them at startup. By default, the content of each register is saved, and will be available next time you run Vim. For example, you might record a macro to register a, then exit from Vim with :q!. On restarting Vim, you can press @a to run the macro from register a.