Please note: I use the pronoun he because it is easier on me than writing he/she or the individual over and over again, but women can be batterers as well as men.
Is he very jealous? At first you think it is flattering to have someone care so much about you. You tell yourself how much they must love you. But then it becomes annoying. And it only keeps getting worse. He's jealous of your family. Of your friends. And forget about having male friends. He will accuse you of infidelities, and you will never convince him that you are innocent. He will be constantly at you, beating you down emotionally and, at times, physically.
Does he have a violent temper? If you feel fear them when they get angry, get yourself away from right away....and stay away before you become a statistic.
Is he easily frustrated and not handle it very well? This goes hand in hand with the above. He becomes enraged over the smallest things--the driver in front is too slow, the line in the store is too long because the 'stupid' clerk doesn't know what she is doing, he thinks someone is looking at him wrong and confronts the individual. Not good.
Does he talk to you in a way that degrades you, makes fun of you, or belittles your accomplishments? Verbal abuse can be just as damaging as physical abuse, and maybe even more so because bruises heal, but painful words can last forever. My ex was verbally abusive. Despite my having a city job while he was a bouncer, he always berated my 'stupid little job'.
Has there been abuse during the courtship period? Don't think you can change him. Break it off right away.
Does he blame others for everything that is wrong in his life? Is he always the victim? One major sigh that a person might be an abuser is them not assuming any responsibility for their behaviors by making themselves out to be the one who is always wronged. Eventually he will start blaming you for everything, and when he does? Abuse will definitely follow.
Have there been any subtle behaviors in the early stage of your relationship? For example, maybe he is a bit too concerned about your safety or questions the decisions you make. Does he know best how you should dress, comb your hair, etc. These type of controlling behaviors only get worse in time.
Does he exhibit times of cruelty and abuse towards children and animals? If they are cruel to them, ask yourself the question. How will they treat me and my children in the future?
What about his childhood? Not everyone, but most people who were raised in an abusive household have a greater chance of exhibiting the same behavior towards their family.