without sounding like a jerk, I'd first say, "If you have to ask......"
But that said, first and foremost is quarantine. Preferably each new frog to its own enclosure. I quarantine all new frogs for at least a month, WC even longer. I keep them on paper towels which are changed every other day (every day if you have the time), and clean out the enclosure at the same time. I prefer to use sweater boxes for this, as they are easy to move around.
After you have them setup in quarantine....
feeding - keep track of how much (or little) the frog is eating
watch for any behaviors that might be a symptom of disease, like scratching, open sores, gaping mouths, etc.
Be ready to consult a vet at the first signs of illness. In fact, it would be better to do so before you even get them so you can have treatments already on hand. Check with Dr. Frye on this, he can set you up with a battery of meds that WC frogs will likely need.
Anyone else want to add?....