I haven't read any of the other replies yet, but one idea that I use when creating (or rather, discovering) characters is to give them little quirks. I always find myself more 'endeared' towards a character who's just a little bit quirky in some way.
An example from a well-known film (as I haven't read any of the books more than once, and that was a while ago) is Pippin from
Lord of the Rings. He's a quirky character in a lot of ways. And so far, I haven't met anyone who dislikes him; and nearly all people I talk to love his character.
Now, I'm sure there are people out there who dislike him. But the majority of people I meet love him.

As for a personal example, I have this character. Rowan is a supporting character in a book I've long since abandoned for now because it was horrible. He's a shapeshifter. But I had to find a way to make him and his counterpart Aelfcynn more endearing.
On a whim, I gave them opposite personalities - she's calculating and serious, and he's bouncy and optimistic. Other quirks he has is an obsession with Skittles and M&Ms, he likes to hug people, and he acts almost like a child sometimes (he's in his mid-twenties human-wise; a much higher number shapeshifter-wise) as far as hyperness and tricks/pranks go.
And I thought people would hate him, but he was well-received by most of the people who read his scenes.
(You actually read the book he was in, come to think of it, I think. The reason Rowan probably sounds unfamiliar is because I changed him a lot after you edited the book, hehe. And I shared the edited version with a few people. They all really liked Rowan...)