I prefer to "prep" my cartomizers for my tanks the same way that I would fill them if I were not going to use them in a tank. A useful tip I came up with is while dripping into the top of the carto, place a wooden tooth pic into the air hole to prevent any juice from accidentally going in there.
The secret of using cartotanks is delivering the proper amount of juice from the tank to the wicking material inside of the cartomizer. This is accomplished via holes in the lower portion of the cartomizer. You could punch your own holes to save a couple of bucks, but for a beginner I recommend that you purchase cartomizers that already have holes in them for the tank setup. This will allow consistancy and takes a big portion of human error out of the equation.
I get my laser-drilled cartomizers in this link
Single Coil XL Tank Cartomizer for the SmokTank XL
but many other online vendors sell them as well as the dual coil variety. I happen to prefer single coil cartomizers for many reasons that I won't go into here. I would order a quantity of both single and two holes. Depending upon the viscosity of the juice you use, the single holes work well with normal thickness 50/50 pg/vg juices. For thicker juices of greater than 60% vg, I use the two hole cartos. Be sure to also order the correct resistance for the battery that you will be using: low, standard, or high.
I also highly recommend that you purchase the tank accessory tool in the below video from Big Daddy Vapor
http://bigdaddyvapor.com/index.php?main_page=product_info&cPath=13&products_id=52.
PBusardo demonstrates how to fill and assemble a cartomizer tank using the SYM tool.