I just push them in until they're fully seated. The molded cap on the end with the cable should prevent them from being pushed in too far. I have also never used any type of lube or anti-seize compound on them, although it's probably not a bad idea. I had to replace one on my wife's '98 Passat and the sucker was completely seized to the point where I had to destroy the sensor to remove it. These things must have about three miles of wire finer than a human hair inside of them.