Keep a few pieces of PVC in the QT so your fish can hide and sleep as required. Like it was mentioned before keep a close eye on your parms in the QT, it can spike quickly. Keep the bottom clean and top-up as required with maybe a small water change every 2 or 3 days and you should do just fine.
As for your fish you buy, have a good look at them in the LFS. Pick the ones you want and make sure you get the ones you want. Watch them at feeding time in the store, have a good look to see if they behave "normally". If you get a healthy fish to start it should help with the QT.
Myself I try and get fish that have been in the store for a while (at least 2 wks) and show no signs of problems then I QT for 2 weeks. Haven't had a problem yet (fingers crossed). It also helps to have a LFS you can trust.
Good luck and make sure your first fish isn't an impluse buy or it might not fit into your plans...stick to your plan...