That's exactly it.Show them you care about them.
We're a selfish species so it's a pretty simple recipe. We tend to:
--- like people who like us,
--- care about people who care about us,
--- respect people who respect us,
--- be interested in people who show (positive) interest in us.
And that isn't a coincidence, there's cause and effect going on there:
"That person likes me. "Therefore interacting with that person makes me feel good about myself.
"Therefore I like being around that person.
"Therefore I like that person".
Of course that doesn't always work. If you're giving attension, time, respect, or anything positive that you have to give and you're not getting it back then you're giving it to the wrong person/people.