Not 30 years, but usually just looking at each other says enough, with maybe a head motion if it's time to go. Facial expressions say a lot on their own, and if you know someone well enough, even subtle differences can say a lot.
Yup, we're only at 12, but a look is enough, we're usually thinking the same thing.
But the other additional one, three squeezes, hands, or whatever can be touched without being obvious, is I love you. Seems sweet, but most often used when one of us is getting pissed off (at something/someone else, not each other).