I have a box with another host that we are using now. I got a monster box yesterday from TP and wanted to know when I should call the other host to discontinue the dns entries and set them up here.

How long does it take? For example if I have the domain test.com pointed to the old host, when should I let TP know to start hosting it? Will it conflict?

Set up the DNS here at TP, test out your site by IP address etc etc. Give it 2 - 24 hours to be safe and then switch the DNS with your domain registrar to point to TP DNS

i.e. tell TP "add dns entry for site.com 127.453.25.66"
Test your new site via the IP
Wait 12 hours.
Edit nameservers in your registrar to point to the new nameservers provided by TP

gp

I would only cancel the old machine after everything been set up on the new machine and the DNS change is activated. The DNS Change over, best to give it 72 hours in case of any hiccups.

You could ping the domain daily and see if it gets pointed to the new IPs. Only then that it is safe to cancel the old machine.

I use http://www.tracert.com Ping and Traceroute feature, if say 80% of the ISP listed there points to the new IP then you are okay.

I sometimes have some unique identifier in the site page on the new machine which is different from the old one. So if I see that something new, I know I am done.