here's the relevant wiki article:
http://en.wikipedia....s_approximation
here's Schlick's original paper from 1994:
http://www.ics.uci.e...s/Schlick94.pdf
and if you're successful with implementing the Schlick method, then you may proceed to more advanced approximations:
http://en.wikipedia....esnel_equations

so for you I think the fresnel term should be:

//Fresnel approximation
float base = 1-dot(f_viewDirection, halfWay);
float exp = pow(base, 5);
float fresnel = fZero + (1 - fZero)*exp;

here's the relevant wiki article:
http://en.wikipedia....s_approximation
here's Schlick's original paper from 1994:
http://www.ics.uci.e...s/Schlick94.pdf
and if you're successful with implementing the Schlick method, then you may proceed to more advanced approximations:
http://en.wikipedia....esnel_equations

here's the relevant wiki article:
http://en.wikipedia....s_approximation
here's Schlick's original papar from 1994:
http://www.ics.uci.edu/~arvo/EECS204/papers/Schlick94.pdf
and if you're successful with implementing the Schlick method, then you may proceed to more advanced approximations:
http://en.wikipedia....esnel_equations

here's the relevant wiki article:
http://en.wikipedia.org/wiki/Schlick%27s_approximation
here's Schlick's original papar from 1994:
www.ics.uci.edu/~arvo/EECS204/papers/Schlick94.pdf
and if you're successful with implementing the Schlick method, then you may proceed to more advanced approximations:
http://en.wikipedia.org/wiki/Fresnel_equations