Dating is an imperfect science. Despite how many stories, lessons learned and pain felt, even today we are still encountering new "happily ever after stories" that what we know and have seen would otherwise tell us, should fail.
That being said, some of the most glaring issues while dating are seen when someone begins dating a person who just got out of a bad break up. Here are some red flags to look for:
1) If they keep talking negatively about their ex, they probably aren't over them.
This is pretty obvious, If they wont stop talking about their ex, thats a BIG red flag that they're not even close to being over them. I will add, know when too much is too much and understand context. If they bring up their ex ever 4+ weeks for the first 3-5 months, thats not quite as evident of an issue as a bi-weekly, or daily mentioning. Also context matters. If they bring them up out of the blue, thats a red flag. However, if it's done when the conversation would make it appropriate, thats not evident of a hang up.