Dancing jellies: how do I strengthen my arms and back to do overhead lifts?

Due to having played soccer in my youth, and many of years of skiing as well as folk dancing, I believe that my legs are strong enough. But I would like to get into some forms of dancing that require lifting one’s partner. I would like to get strong enough not to be too embarrassed even before I start.
So, I ask my fellow dancing jellies, what specific exercises do you recommend to strengthen my arms and torso for lifts? (I have access to a gym.)
I suspect that it may be matter of both strength and technique. So what do you recommend by way of technique? How do those guys do it? (You can see this figure skating, too.)