I'm always stressing to check a kick and invariably I see all of my guys do a half ass job. Toes up or down, I just be happy to see them do what they are told.
Toes up in my opinion.
every trainer teaches it differently...i was taught that instead of checking it with your chin...step into it and catch it on your lead thigh. this allows you to close the distance greatly and counter with your cross. john hackelman implements this as well as my teacher shawn tompkins did
step into it and catch it on your lead thigh.
Make it slide up your thigh IMHO.
same thing...
Kyokushin karate generally teach toes down (and elbow slightly overlapping on the outside of the knee). But several kyokushin offshots teach toes up (ashihara, enshin and a few others).
Another popular method is to step into it like ninja 316 suggest and catching it on your tight while tensing it. This is especially popular among larger fighters. It is faster, dont open you up to be swept of your feet and gets you in close where knockdown karate guys (esp large ones) prefer to be -but it is not as good as the shinblock and demands that you can take a hit (or ten)