Think about the books you've loved. Chances are, they were hard to put down because you had to find out what happened next. And you had to find out what happened next because you cared about the characters in the story. Sometimes, characters can be so compelling that they stay with you even after you've finished the last chapter and put the book on the shelf.
Imagine this opening scene: the main character (we'll call her Jane) is straddling the rail of a bridge looking down at the churning river water and deciding whether or not she should jump. It seems that Jane has been accused of the murder of her boyfriend John and the police are looking for her. That's a pretty compelling plot line and it may be enough to get you, the reader, to read to a chapter or two. But chances are that if you don't start caring about Jane in those opening chapters, you'll put down the book. If you don't connect with Jane in some way, you might not pick the book up again.
How do you make the reader care about your characters? Let's use Jane as an example as we examine some of the ways this can be done
* Give Jane a sense of humor. There she is, sitting on the rail, and thinking; Jumping will ruin my hair. The mortician will have one hell of a job blowing it out.
*Make Jane Heroic. There she is, on the rail, when someone else comes along and wants to jump. Jane talks the other jumper out of it. Or, when the other jumper jumps, Jane jumps in after her and saves her life.
* Put the odds against Jane. We find out that Jane killed John in self-defense.
*Make Jane smart. She climbs under the bridge and drops her coat and a rock in the water.
*Make Jane redeemable. Yes, she killed John in a moment of passion, but she's feeling very guilty about it. She's thinking should turn herself in and face the consequences.
*Make Jane fascinating. Maybe Jane isn't likable at all. Maybe she's a serial killer. But she's so evil that she's fascinating. (In this case, we're rooting that she gets caught)
The point here is that the main character has to be compelling enough for the reader to read on. So, make those characters compelling. Make the reader care about your characters.