I am traveling to Vietnam/China. How can i get my US cell phone to work over there?

My service provider is verizon wireless and i am using a motorola razr v3. what can you guys tell me about traveling with cellphone? is there a specific type of phone that would work worldwide?

satalite phones work everywhere

If you have a triband cell phone (most are tribands now-at least) and have GSM it will work worldwide - except Japan, where I believe you need a Quadband.
you need to call verizon and allow out of country roaming for call placing and call receiving. Then when you get to the country, the cell phone will automatically search for local providers and you can make and receive calls.
An alternative is to buy a local SIM card and insert it and make local calls for local prices. (buy a prepaid card)
This only works though, if your cell phone is "unlocked", which it should be if you bought it independently, if you got it with a contract it may not be, which means it would not accept a "foreign" SIM card. Take it to a dealer to find out.
In general traveling with a cell phone is great, a lot of providers give out coverage maps of the country you plan to travel to... Just watch the costs, as receiving calls (f.e. from the US also costs money and calls to the US can be expensive, so you just have to know the costs and watch it a little, so that you don't get a $700 phone bill!

If you are not on any plan with your service provider, then I think you can buy a simcard in any city in VN and put it in your cell phone. You can buy a prepaid card from a variety of shops in Saigon, but I think it would be better if you have a friend there and ask him where is the best to buy. There are at least four service providers but I am not sure if you can call someone in the US with a simcard bought there. My brother in VN often calls his sister in the US by landline phone. The best way is to ask a post office and they can give you the exact answer.

Enjoy your visit.

satellite phone works everywhere. you can ask your provider for a roaming. the other option is buy a sim card that you can temporary use in that country as long as your unit is tri band and open line