I'm going to preface this with I am a survivor of domestic abuse and I volunteer at DV shelters - so here is what we know to be signs:

Controlling behavior - they don't like your dress, they don't want you hanging out with your friends, etc.
Isolation - they suddenly find fault with your family and friends and seek to isolate you from them
Reckless driving, angry driving <-- this is a very common feature of most abusers.
Unreasonable jealousy - they call relentlessly when you go out with friends, accuse you of cheating all the time.
Hypersensitivity - they are generally very sensitive to any criticism and often find criticism where there was none intended.
Breaking or striking objects/threatening violence/history of abuse in their past(as victim or abuser)
Quick involvement - most abusers want to rush a relationship - they are prone to wanting to move in together and get engaged very quickly (it is a defense mechanism because they are afraid you find out who they really are)

There are many many others but here's a tip - if you are asking this question about someone in particular 9/10 he is an abuser. I highly recommend you call or visit the National Domestic Violence website for more information

I agree completely with Mary, the only thing that I would add is that often (in my experience, at least), verbal aggressiveness is a precursor of physical abuse. Emotional wounds caused by these words can be just as severe as the effects of physical violence. That and I'd like to add that often, men who accuse YOU of cheating are doing so themselves.

Honestly, up front, NICE guys have turned out to be the WORST for me. Guys that are friends or can joke around with you seem to less often turn out to be good guys. I don't like the whole "good guy" concept. Guys that seem great right up front are often just doing that... Putting up a front.

I would be concerned with the fallowing:
--Guys who NEED a beer every time you go out and stay in AND when he goes out with friends. (now if you're going to a bar or the game's on or being romantic with wine that's different!) Even if it's just one or two and they're not drunk... It's a bad sign. That's a waste of money and often a huge flag for future alcoholism or money management issues. This isn't always the case... So don't be too judgmental. This defiantly needs to be asked with a few questions. Why does he feel the need to drink? Is it always or in certain areas/with certain foods? Where else does their money go? Are they struggling financially or do they just do this on special, not as often occasions and save their money the rest of the time?

--They call out your skanky girl friend. Let's face it... Most of us have the one girl friend in our pack that is a little out there. Hanging all over guys, getting trashed, looking for attention. It may be subtle or extreme. If he calls her out on it too soon it's a quick sign he's someone who judges quickly. I had a guy who called my friend a skank for sitting in our mutual friends lap. "She has a bf. That's wrong, she's a slut." This was only the second time he met her and it seemed very judgmental and eventually led to him judging me and not trusting me. He told me I couldn't hang out with her. Possessive guys are dangerous.

--Making ultimatums. When a guy makes you choose between him and your best guy friend out of jealousy... BAD sign. Any time he MAKES you choose is bad. He's a control freak.

--Freaking out about you spending the night or having sex because he wants you to... If it's early enough in the relationship neither should happen. A good guy would wait or understand if you didn't want to do either or do it all the time.

--Guilt trips. Guys who make you feel bad for not spending enough time with him, because you're in work/school usually end up abusive and controlling, trying to turn it around on you to make you feel like it's your fault. GET OUT!
--Emotional freak outs. (Goes somewhat with guilt trips.) Insecure guys can turn out crazy and get abusive a possessive if they don't feel loved. Guys that call you a b*tch or freak out in fights right away as a defense mechanism instead of talking out situations tend to be abusive as well.

Good luck with finding a boyfriend and potential father! Someone is out there for you, just be cautious! :o)

if your a single mum, and hes trying overly hard to play daddy to your child be careful he doesnt throw this back at you at a later date as a way to control you,

because you already have a child be careful not to fall pregnant to quickly as again this is a way to trap you

if he tells little white lies to you and turns it back on you when you find out 'its your fault you dont trust me, i just wont bother telling you anything from now on and god help you if you try to question me' this is common

if he drinks regularly this is also a big warning sign as they try to blame there actions on drink or drugs - if this is true why arent most of the nation killing each other on a friday night, only the minority get aggressive.

i was a single mum when i met my ex, i feel pregnant very quickly, the warning bells were only slightly ringing in my head and i chose to ignore them, four years later im now on my own and really mentally and emotionally screwed up along with my kids, if your asking this question already get out before you end up in a bad situation.

i had little niggling worries but ignored them, he pulled a knife on me at 40 weeks pregnant which has the first big incident after months of little signs like lying, drinking etc but nothing to really make me think get out. its had a lasting effect on my eldest who saw it and the child i was pregnant to as my placenta ruptured luckily they saved her.

i wished id walked away at the beginning as i wouldnt be struggling to teach my sons thats not the way a man should be (theyre already extremely manipulative themselves as its what theve grown up seeing)

it started with constant compliments, progressed to put downs, lies, threats etc, then fists through walls, things getting smashed and knifes being waved around but progressed to physical abuse. after my third child was born i was always told no one else would ever want me as i was ruined he loved me despite of this as i was ruined having his kids etc. he didnt like me wearing make up or low cut tops as it 'made me luck slutty'

walk away for the sake of your child before the damage is done, take it from some one that is really struggling on a daily basis to get her and her kids lives back on track

if i had known the warning signs at the beginning maybe i wouldnt be in such a mess now unable to sleep for fear hes gonna turn up again (he always does tapping on my windows or trying to break in, good luck, only you can decide what you want to do but look at your child and think do i want to risk him having mental health problems through life because of the decisions i am making in the present

Mandatory reading for understanding your world.
http://www.heartlessbitches.com/rants/niceguys/ng.shtml
You can avoid a ton of mistakes if you camp out this site.