I'm shopping for cloud hosting for my forum and will need to move my existing domain name to the new cloud hosting forum when I buy it. Please tell me how this is done so that I don't lose my traffic to my site.
You would want to transfer the domain at the time of purchase. And, this should be an option when you are signing up. They will ask you to choose a new domain name or transfer one. And, the procedure will be handled by your company.
I would recommend transferring your domain when you sign up because if you wait, then you will have to change the DNS/name servers on your own. Ask your hosting company for help or tutorials if you need to know more as their procedure may differ from what you are accustomed to now.
There are different ways to change the domain's hosting. You will first have to confirm from the cloudd hosting provider as to what type of domain is available and then go for that.
Here is a great list of hosting providers.
Usually when you purchase a domain you'll have to wait 30-90 days in order to transfer the domain, although you can always transfer the hosting to a new provider. The how to do it simple depends on the control panel being used or software the hosting is on.