Pretty much every judoka that has ever lived has gone through the process of learning some combinations. Some particular combos are so blatantly obvious (like kouchi-ouchi) that they are documented from way back and everybody works on them, and other combos are so novel and interesting and creative (like seoinage-nidan kosotogari - A.K.A. "The Twitch") that when you see someone throw them in a match it makes you want to go out and work on those combos. Both of these types of combos tend to pass rapidly into the collective memory. Everybody works on them and everybody tries them in tournaments (but consequently, more people have experience countering them).
Even though throwing classically known combos can get you busted, it's not bad to work on some of them. A pretty good list of combos can be found at JudoInfo. I like this list because it is basically a bunch of three-step combos - it has both setups and follow-ups for lots of techniques. Some of my favorites include...
- ouchi-kouchi-seoinage (or taiotoshi)
This weekend I get the privilege of teaching the Fall Seminar at Union University in Jackson, TN. One of the topics they called for is how to put combos together. So I figured since these are college folks They would probably enjoy a touch of homework...
Brown belt Unionites, before this weekend, look over Ohlenkamp's list of classically-known combos and find 1-2 that pique your interest. Try to pick combos using techniques that are about your level and for simplicity, let's avoid counters and sacrifices. Then we'll spend some time Saturday PM working through your combos that you picked and trying to figure out how to put them together using the system and method that I've been blogging about for the last few days.