Just a general comment... as Phi mentioned... relaxing, or rather releasing tension is a key prerequisite. In ICMA, fang song means "to loosen", which in effect means, devoid of tension - like say, a rubber band, or a spring, at rest.
From Taijiquan: Through the Western Gate" by Rick Barrett
"The physical extension of a body part is preceded by its insubstantial correlate, called fang in Chinese. Fang is "reaching" with the mind, extending awareness before actually extending an arm or leg.
The substantial aspect of taiji power is derived from the body's tensegrity (song). It is easily triggered by pointing the index fingers and reaching (fang). Pointing and reaching establish the boundaries of the body's "tent". Relaxing into the structure that is formed keeps tense muscles from choking off the flow of qi."