I don't know what you've been told thus far, and I don't know what your set up is like, so I'll start from the top... If you can describe your set up, or get pictures I could help more specifically.

First is your enclosure plastic or glass? If it's glass, humidity and heat are harder to keep up, but by no means impossible. If it is glass you may want to consider closing up the top a little bit.

What is the heat gradient?
How is the enclosure covered?
Heat Sources?
Water dish size?

- The first thing I would look at would be the size of the water dish. One with slightly more water surface area can help increase humidity.

- Also putting the water dish closer to the warm side can help too. If you have a Heat lamp or Ceramic Heat Emitter, those can decrease humidity slightly.

- Something else is a possibility. If your temps are too cold it won't be as humid.

- Substrate can also make a big difference in the amount of humidity in the air. Some sub. just suck the humidity up, others release it slowly. Jungle type bedding is good to keep humidity up, and coconut bark is good also.

You would be surprised how dry it is, depending on where you live. During the winter air is dry naturally, during the summer it's humid outside, but the AC drys the air out.

Hope this helps.

J