maybe the most common way is to add the command to your init files so it gets read and started at the init part of the boot process....one "good" file is rc.local which resides (possibly) in /etc/rc.local and any commands put into this file are launched after all the other init commands....
there are also runlevel-dependent init files, but check out the rc.local first

then get to know the rest of the family...and files that reside in /etc/rc.d/ too