TWK:
What are some character traits that will make the reader sympathetic to my characters? I tend to make them (my characters) rather dry, and I don't usually give them redeeming qualities—because I'm not sure how to do this.
IMHO, whether a character comes across as being sympathetic is something that's addressed more in the writing (e.g. how they react to particular situations and how they talk to other people) rather than trying to shoehorn character traits into them.
For example, if your character is aggressive and abusive in every scene that they're in, they're going to come across as a schmuck. But if you have a scene where that character is victimised at home or by someone in authority, thereby showing that they are also vulnerable, then it can help the reader understand why they are like that with other people.
To give another example, you could have a cold dispassionate teenage killer who'll take a moment to pat a dog on the way out from a hit. Or the flip side is the saccharine sweet popular girl at school, who secretly writes abusive anonymous emails and sets out hate websites against other kids.
Basically, it's a process of evolution rather than ticking boxes.
Also, you say that your characters are "dry". That to me suggests that they're not coming alive on the page rather than that they lack redeeming qualities. Without seeing a sample of your writing, it's difficult to make an assessment, but again, it's a question of evolution in the page, building in the little traits and niggles into a character that helps them seem more fleshed out.
MM