If u're not into weird tunings or you're not using a baritone, then your guitar should be tuned EADGBE or BEADGBE for 7 strings (perfect 4th intervals with a 3rd on 2nd string B)
A standard bass would be EADG or BEADG (5 string) or BEADGB (6 string).. so ..do the math and tune from there...(ps: any more strings and u're being fancy!!)
Agree, that they shld tune to each other. I'd rather tune to keyboards though if given the choice, coz they're the most precise in my mind...
Then again, tuning is like an expression...u can always tune ur guitar differently, or 1/6th a step down from the rest to create some out of this world sounds...