White Walkers HAVE to be able to talk....They had a deal with that dude fukking his daughters and offering his newborn sons to them... How the fukk was that deal struck?...Where did he learn screech talk?....
I bet they communicate telepathically and have a hive mind...
The giants, children of the forest, white walkers, ect all have their own languages. There is also a common language called the "old tongue", which lets different speaking clans communicate with each other. Kind of like how North America has people speaking in all kinds of different languages, but English is the one that is universally understood by almost everyone. Although not as many people know the "old tongue" north of the wall anymore - so maybe Latin is a better example than English.
As far as Craster goes, I personally think he just stumbled on the deal. One day a scary ass white walker just walked into Craster's house, snatched up his son, gave him one of those terrifying murder looks, but didn't hurt or kill him. Then it happened again. And again. And again. And kept happening until Craster figured out that he needed to donate his sons to the cause.