There's a variety of things to think about with skins, but if you're just getting into touring or don't tour that much, you probably won't notice many differences between the options.
Three main materials: nylon, nylon/mohair mix, and pure mohair. Nylon is the most durable, while mohair glides the best. The mix is exactly that: a mix of durability and glide. The mix what I tend to use on my gear.
Tip and tail connectors are another question. G3 makes better ones for rounded tips and tails, yet they can be a little less adjustable than the BD version (say you need to shorten your skin). So you can think about that.
Pomoca has been making a strong entrance into the US market, and they make the precut skins for a number of brands (Dynafit, K2, Volkl, Line). Their glue doesn't seem as robust as the G3/BD options, but I've seen them glide perfectly in snow temperatures that had everyone else glopping like crazy (snow sticking to the skins and inhibiting glide).
For someone who is just looking to get out and get started, find a nylon option that's cheap and offers a good tip/tail connector.