This is so much more than most would realise at first glance.
First let's focus on the planet itself. As Xavon pointed out, there would be a scorched wasteland on the 'bright' side, and a frozen wasteland on the 'dark' side. Look up some information on Ryloth (from Star Wars Expanded universe). What would this mean for your planet? Well, as already pointed out, the most logical place for life to start is in the regions between the two extremes.
Note, life would 'START' in the twilight band, it wouldn't be only there. So long as there is a starting platform, extremophiles will migrate and given enough time (millions and millions of years, I'm sure everyone knows the evolutionary shtick) could evolve into higher lifeforms.
Second, local weather would be chaotic because of these two extremes. The hot air from the bright side would expand, and try to flood into the cooler dark side (air pressures trying to find an equilibrium). But the energy wouldn't be lost, and cold air would eventually try to trickle back to the warmer side. This would mean there aren't 'seasons' as we know them. Everything would be considerably more chaotic, changing by the day. Any life that forms would have to be hardy. Plant life, microbial life, wild life, your sapient life -- everyone needs to be tough as nails to survive on a planet like that.
In all likelihood, just as in the Ryloth example, cities would form underground. I mean, if the outside world is so chaotic? They'd need a stable place to call home. It would no doubt lead to highly social groups, seeing as they need to depend on each other to survive, and to raise the young if something happens to the parents. There would most likely be fungi and meats to feast on (their staple food, seeing as both could grow naturally in caves where they call home), and there would likely be hunting parties that go out into that big, bad, chaotic world to see what they can see.
There are also a lot of other factors that would/could come into play, like the culture revolving around what scant food there is (as is the case in my example) which leads to fat people being considered rich, leaders (and this is a real world example, if you look at certain African countries, India, the Middle East, fat doesn't have the same stigma as in the West).
EDIT: You won't find cold-blooded beings in a world (or region, if you want to get specific) without sunlight. Seeing as they cannot regulate their own body temperatures, they cannot hope to survive without a source of heat. Expect warm-blooded creatures, and furthermore you can even expect hairy/furry creatures with excellent night vision, excellent sense of smell and hearing, and lots of excess fat.
Why? Fur helps keep warmth in, losing less energy to the frigid air around them. Fat retains heat as well. With no light, they need other means of studying the world around them--hence the other senses will be heightened. I suspect no one answered your original question, because you didn't google life here on earth, or the science behind cold-blooded animals. Cold-blooded animals need sunlight, need warmth, need a means to regulate their temperature (as I already stated). This necessitates a heat source, by definition.