Sexily! And usually mostly undressed or at least topless.
More seriously, I've always liked the version of Steve Trevor who was a military man, but who became disillusioned by the work and experienced too much heartache, so he became a humanitarian of sorts (albeit one with superior piloting and military skills which were used to further his aid missions). I like Steve to be flawed and imperfect, but trying to do what is best anyway. Steve should be "above-average" for a human, but still a "damsel in distress" because we're talking about comic books and Wonder Woman is *the* hero. That doesn't mean that Steve shouldn't have his own heroic moments, but never at the expense of Diana's character.
I'm happy for him to have a sense of humour, but he doesn't need to be quipping all over the place like Green Lantern or Spider-Man. And I'm happy for him to be a "hero", but that doesn't mean he's practically perfect in every way like Captain America or Superman. Steve should be human. His flaws should be acknowledged and complimented by and contrasted with Diana's own flaws and personality foibles. I definitely don't want him to be sexist, chauvinistic or arrogant. Maybe he was back in his military days, but he should be far beyond that now and fully supportive of Diana and her work as Wonder Woman.
I do think that there should be an interesting tension between Steve and Diana about their future - does Diana want children and, if so, when; Diana is immortal and Steve is mortal, so how do they actually envision their future together; Diana is away a LOT and although some of her away missions may mean working together with Steve or assisting his humanitarian efforts, there is still a lot of time spent apart; Diana comes from a world of myth and magic whereas Steve is a down to Earth military man, so what does that mean for their perspectives on life and love?