Throwing contrasting characters together, like the mild-mannered loser and the confident cop with a gambling problem.
What didn't work:
Having the mild-mannered loser move in with the cop simply to provide contrast and tension. This wasn't set up well at all. Characters often did not act realistically in general.
After the hostage ordeal, one couple breaks apart even though they had seemed very happy. We later learn it's because the man took a chance and tried to escape, leaving his girlfriend behind.
This part was told at a dinner. Not in a flashback, although the show is half flashbacks anyway. Haven't the writers heard, "Show, don't tell"? All the dramatic tension got leaked away.
For my one TV show I'm watching, I'm now trying Day Break. It's Groundhogs Day meets thriller. A cop keeps reliving his day, which goes terribly wrong each time. Most days his girlfriend is killed, or his partner, or both. He is framed for a murder, sees other people shot, finds dead bodies. And then he wakes up again in the very same and tries to piece it all together and avoid the previous bad things. For the writers, it must be fun to think of all the possibilities. They just didn't grab one thing and go with it. It reminds me how many different directions a story could go, if I would just think about it for a minute.