1. Ensure there is something about your characters that your readers can identify with. They don't necessarily have to agree with your characters but should be able to see why your characters are acting as they are. Part of the challenge of a story is to get your readers to wonder whether they would have done the same as your characters and, if not, why not and what would they have done!
2. The goal should be an understandable one. From the character's viewpoint, naturally, it has to be a life or death matter. It should be something they are prepared to risk all for. It should be something they can't refuse to do.
3. Characters should be memorable. Doesn't matter if they're heroes or villains, the crucial point is your characters should stay in the minds of your readers long after they've finished your story.