There are a few things to consider completing before installing your manifold. These things are by no means necessary, but may save you some headaches in the future and will make the swap better in the long run. Basically, these are things you can do to make it so you are essentially installing a brand new, ready-to-go manifold.
The VIAS
-Right off the bat, you should be testing the VIAS that came with your manifold. You can test it by hooking up a hose to the metal nipple on the front of the VIAS (the left one if you're looking a VIAS with two nipples on the front), and sucking through the hose with your mouth. If you see the arm on the solenoid move, then it is working properly. If not, you may need to seek out a new VIAS unit that DOES work. Don't worry if the arm doesn't go up the whole way, it's doubtful you can suck as hard with your lungs as your engine can under load.
-Assuming your VIAS is atleast moving the solenoid's arm, the next step is to check if the VIAS to power rod "cup" is still in one piece. This is a part that frequently breaks on these manifolds, so it's good to check this out beforehand. While performing the same test as you just did to see if the VIAS is functioning properly, look inside the manifold (from the bottom through the ports) to see if the power rod rotates as the solenoid arm moves. If not, your cup is broken. But can be fixed using the VIAS fix listed on the main page of the 00VI section of this site. Even if your cup is not broken, it is a good idea to do this "fix" as a precaution to prevent it from breaking.
-Since you'll likely be taking the VIAS off of the manifold for one reason or another during this "check-up," you should replace the 4 bolts holding it on as well. The OEM ones are Phillips head brass bolts, which strip easily. Replacing them with hex head bolts of a different material is a safe measure for future removal of the VIAS.
The Manifold Itself
-Cleaning of the manifold is a good thing to do before installation, as well. Lots of sludge and carbon build up in the manifold as a result of the EGR and PCV systems. You can clean them with a variety of things, including throttlebody cleaner and ---.