Block for Low Punches
Block your opponent's arm with your forearm and follow through with a counter-punch above the other person’s arm.
Interception Punch
Block your opponent’s punch with one arm. Counter with a punch with your opposite hand, drawing power through your back foot.
Peak Punch
Block your opponents punch by deflecting your opponent’s punch off your forearm. You can counter with a punch of your own or use a front kick to knock your opponent back.
Tan Sao
Block your opponent’s punch with your forearm. Your open palm should face the ceiling during the block. Counter with a punch to the head or ribs.
References
http://www.functionalselfdefense.org/wing-chun/
http://sifuochwingchun.com/4-ways-to-intercept/