Another good little book I bought a bit ago, "The CTX 3030 Survival Guide". By, C.& R. AURUM. It's a great little addition and I find myself thumbing thru it still. Jason is correct, pick a mode and stick with it. Get used to what the machine is saying.
I started with the stock coin program. I then downloaded Gone Huntings combined mode, I use that (slightly modified) almost exclusively now. I recently got Andy's book and intend to try a couple of those modes. If you join the CTX users group on this forum, in community, Mike Guard has put up a list of "typical" numbers for various objects. It's helpful when setting up a disc pattern.
Bottom line, sounds are your friend. You'll learn to hear the difference between wrap around and halo's, for the most part anyway. I still dig the occasional bent nail or the like, so what. Aluminum still occasionally gets my juices going however. But for the most part, you'll get familiar with the difference between a true hit and a can/lid etc. Wait till ya hit an aluminum horse shoe, you'll swear you're in the money.
You will love this machine once you get in the zone with it.