I'm moving all my clients to a new host, as well as my site. Currently I have them using my domain as the nameserver, which I set up on the old host. If I change the nameserver of my web site to point to the new hosting, will my clients sites still be directed to the old host until I move them? Should I move them all at once?

Thanks!
- Jae

You should have the client files at both hosts. Don't cancel your old web hosting account until the move is complete.

After you are sure you have the data at both hosts, change your domain name servers to your new host. It will take a couple of days until all traffic is going to your new host (until this time people may still be going to your old host).

If you've found a good host, they'll usually assist you with the move.

what webfreak said is right, just move everything first, then you change the ip for nameserver in the registrar