I have seen a lot of hype around selling and buying of domains. Is it profitable? how to decide which domains to rgister or which not.

It depends on how wisely you invest (a little on luck too). I think joining few domain forums and asking tips from other members will be a good start. Also read few articles on domain trading. You can finds hundreds by searching on google.

domins are profitable if you have an experience in this field
you need to read forums posts and have to chat with others and see wht they buy etc

It’s definately a profitable business, the main problem is you need to really put a lot of time and effort into learning about domains in general.

you must research first before entering the domain name buying field, I would also have to say that a certain amount of what you learn is going to come from mistakes you make.