How to choose a good calligraphy brushChoosing the right brush and correct way of holdling a brush are the most critical aspects of making progress in practicing calligraphy.
The four criteria for choosing a good brush are:
1. "Pointedness" means it should be as sharp or pointed as an awl.
2. "Roundness" means the tip must be in the center of the circle.

3. "Evenness" means that when you spread the brush hairs and hold it down, the hairs are even but not scattered.
4. "Strength" means the tip of brush hairs is flexible or elastic. For a brush to be strong, it must contain enough number of hairs to be solid. If we squeeze the root of the hairs and it feels hollow, it's not a sold brush and it won't produce enough strength at its tip during writing.
More details may be found in:
http://www.art-virtue.com/basics/ChoosingBrush.htmhttp://www.art-virtue.com/principles/index.htm#1