The principle of Wing Chun is to get close to your opponent so that you can maintain contact for defensive practicalities (think Chi Sao) as well as creating openings (think trapping) that enables you to strike your opponent at will (think chain punching, elbows, finger strikes, open hand strikes, leg stamps, etc, etc.).
What that means is that in order to be effective you need to close the gap between you and your opponent without getting pummeled with kicks. There are a few things that I would suggest you concentrate on in order to achieve this. They are distance, footwork, blocks, intercepts and counters.
You must understand the different distances in a fight scenario, typically they can be broken down into the following:
Committed kicking range
Short kicking range
Committed hand striking range
Short hand striking range
Okay, the first thing you will probably notice is that I do not use the usual standard of kicking range, punching range and grappling range and there is a reason for that. There is too much variance in each of these three ranges to effectively practice your movement, it is limiting to do so and we train to expand our knowledge and abilities. The seven ranges I have listed all can cross over one another and is dependant upon many factors the most obvious being the size and abilities of your opponent.
It is important to train against opponents of varying sizes as this will greatly change the way in which you will have to respond. For example if someone who is kicking you stands at 5'1" you may be able to get into trapping range with one step but against someone who is 6'4" you may need explode in differently or take an additional step.
OPTIONS FOR CLOSING THE DISTANCE
There are three initial options for you:
1. Close the gap before the kick is launched
2. Avoid the kick and close the distance
3. Block/Intercept the kick and close the distance
Again each of these options should be practiced at all of the different distances from which kicks are delivered.
The best option always is to get to the distance you want to fight at prior to any incoming kicks being delivered, this means quick, efficient and effective footwork.
Next preference is to avoid the kick and close the distance, again this is dependant upon quick, efficient and effective footwork.
Finally, if you cannot choose options 1 or 2 then you have to block or intercept the kick and close the distance. The reason I put this as your last choice is that you are more likely to get hit with this option than with the first two.
THINGS TO CONSIDER
What type of kick is it? You do not want to try and block a thai kick to your head with a tan sao for example (I know of two people who broke their arms trying to block thai round kicks with their arms so this comes from experience!). No matter how good you think you are at blocking and redirecting the oncoming force you can get caught out and your arm is no match for a well delivered thai round kick.
How early do you see the kick? The earlier you see the kick the better, what you want to try and do is stop the kick from being delivered at the earliest point from release. This typically means as soon as the foot is leaving the ground you want to block it with your foot or intercept it with your own kick.
How do I block the kick? Once a kick is on its way your block does not need to be powerful if you are quick as there will be little power built into your opponents kick at the beginning of their kicking motion. This is often referred to as the arc of power, the key thing to remember is block it early. Block kicks with your lead foot whenever possible, this is the most effective tool you can use to block the kicks as it is the closest to the start of your opponents kicking foot and so has a shorter distance to travel, from the first day of training in Wing Chun you learn about economy of motion and this is a prime example. You can jab your foot into the kick to stop it or you can deflect the incoming kick with your foot/leg.
If you are blocking with your hand/arm then deflect the kick and do not resist the kick.
Never try to meet a kick with force when blocking with your hand/arm as this can lead to the 'blocked' kick taking out one of your weapons and a long wait at the hospital to fix your arm. A good rule of thumb is to deflect the kicking leg at the sides of the leg (imagine two lines running down the insides and outsides of the thighs to the ankle) for example on a front kick you would deflect the power to either the left or right hand side and not try to deflect it by contacting the top of the kick as the power from the kick could pass through the block and make contact, the same principle for a side kick deflect the power at the side of the leg forcing the leg downwards and not meeting it at the front of the leg head on.
How do I intercept the kick? This is simply where your opponent launches a kick and you deploy a quicker more direct kick to strike your opponent before his kick can be completed. A favorite of the Wing Chun student is a kick to the standing leg for example if your opponent is launching a round kick with his rear leg then you would deliver a short direct stamp to his supporting knee. Another very effective intercept which is unique to the Wing Chun system is the targeting of the inside of the hips. This again is very effective against round kicks and can be delivered to either hip, this has the effect of not only damaging the hip joint but also dropping your opponents torso forward open for effective striking. Intercept kicks using the same principle as you do your Wing Chun hand intercepts, the shortest travel route between your striking tool and your opponent, this means a straight line.
A kick that is well delivered is a devastating weapon if it makes contact but it is also a lot easier to defend against than many of the hand strikes that you will be using once you do avoid, block or intercept their kicks however you must practice against them or you will get caught out especially against kicks to the knees. The Wing Chun stance is suited perfectly to defending all manner of kicks, it is up to you to use it wisely and train for that moment.