Humidity levels
Cleanliness
Food
Cover

Tree frogs generally spend most of their time in the tree canopy as apposed to the forest floor. Because of this they are subjected to good air circulation which in turn means lower humidity levels. 85% to 100% for prolonged periods can cause the development of bacterial or fungal infections.
(Use of a rain chamber when breeding is the exception.)
Enclosure's must be cleaned regularly. This is a must because waste which if left in the tank will heighten mold and bacterial levels.
Crickets are the main readily available food although some people feed roaches and other insects.
Tough leafy plants where the frogs can hide help reduce stress and provide eating and sleeping platforms.

What works for me:
I keep the frogs in a Exo-Terra 18x18x24 tall or regular aquarium a computer fan. The The Exo-Terra naturally has enough air flow to fulfill my frogs fresh air needs.
When I kept my A. Annae in a planted tank I found it was hard to keep mold levels at bay. Paper towels were the most sanitary and economical substrate I found. One can see that they are visually clean and when the entire tank is misted before lights out, they help provide humidity during the night. I sometimes also mist in the morning before I go to work if the paper towels look to dry. Some people also like to provide the frogs with a 1/4" or less of water in a dish to give them a soaking spot.
I like to feed 3-5 1/4" to 1/2" crickets per frog every or every other evening. Alternated dusting with Rapashi products provide vitamins and minerals as does feeding crickets healthy foods. I use Josh's frogs cricket feed. I quit using potatoes and lettuce as cricket feed because of this cause a lot of feeder deaths.

I hope everyone finds this post is helpful.
Good luck,
Seth