Pretty much everything has been covered but I just want to reiterate cause I've worked on the lake and seen a lot. Would highly recommend a two cable system. And when attaching the two cables use a shackle for each cable attached to the buoy. Doesn't do much good to have two cables going to the same shackle...then your backup system is irrelevant when the pin backs out and you go floating to the beach. I've never seen a newer cable snap so the only worry with breaking a cable is after a couple years. Inspect your cables and make sure they aren't rusting or fraying. This can be hard if you have the plastic cover over the cable but you can still check for kinks in the cable/plastic or see if you see any signs of rusting on the parts of the cable that are showing at either end. Like others have mentioned, use some nice bailing wire and wrap it through the hole in the pin and around through the inside of the shackle a few times to keep the pin from backing out. In my experience it's about 50/50 old broken cables or a shackle pin that's backed out. Give me a bit and I'll see if I can't find some pics of the hardware and buoy setups we used. It's also a good habit to check the bailing wire everytime you are at the boat and check your shackles and other hardware of the buoy to make sure nothing is getting worn through. Years and years of metal rubbing together takes it's toll!
Also boat poles can be nice if it's decently calm and you have time to slowly approach the ball and haul up one of the cables and attach it while still drifting, but in many cases, especially when doing it alone, we would just attach a 10' or so rope to the front of the boat and loop it through the shackle/eye of the buoy and then tie it back off on the boat. That way you are somewhat secure to the ball while you mess with attaching your hardware.