You mean you plan on using a VPS to host your Magento site.
Be sure to check the server specs. You will want a higher end server. A dedicated server would be better as you might need the speed / bandwidth (Magento is a resource hog). Be sure to tweak your sql settings.
I suggest http://www.servint.net - They have superb customer service and great servers (be prepared to pay $50+ per month).
Make sure you have PHP 5.2.x installed, apache (of course), pdo_mysql.
If you are the root user of the VPS, which I am assuming you are in the above info, (that is, if you are in control of the server, and aren’t one of the accounts on the VPS) you will have the power to change PHP, etc, to make Magento work (for instance, if you dont’ have pdo_mysql).
If you are just an account on the VPS and going through a reseller, then you have to make sure you have the proper plugins, etc and can get them if you don’t have them available.
If you are just one account of many on someone’s VPS, I suggest getting your own server (my server recommendation above still holds).
Hopes this makes sense!